add new rtl vmwip-rtl-vm

* libguile/vm-engine.c (rtl_vm_engine): Add new VM.
  (vm_engine): Add support for calling RTL programs.

* libguile/tags.h (scm_tc7_rtl_program): New type for procedures that
  run on the new VM.
* libguile/evalext.c (scm_self_evaluating_p):
* libguile/goops.c (scm_class_of):
* libguile/print.c (iprin1):
* libguile/procprop.c (scm_i_procedure_arity):
* libguile/procs.c (scm_procedure_p): Add hooks for the new tc7.

* libguile/programs.h:
* libguile/programs.c (scm_make_rtl_program, scm_i_rtl_program_print)
  (scm_rtl_program_p, scm_rtl_program_code):
* module/system/vm/program.scm: Add constructors and accessors for the
  new "RTL programs".

* libguile/vm.c (rtl_boot_continuation): Define a boot program.
  (rtl_apply, rtl_values): New static RTL programs.

* libguile/frames.c (scm_frame_num_locals): Adapt for frames of RTL
  programs.

* libguile/frames.h: Add description of RTL frames.

* libguile/Makefile.am: Add rules to generate vm-operations.h.
* .gitignore: Ignore vm-operations.h.
* module/system/vm/instruction.scm:
* libguile/instructions.c:
* libguile/instructions.h: Use vm-operations.h to define enumerated
  values for the new RTL opcodes.  Define some helper macros to pack and
  unpack 32-bit instruction words.
  (rtl-instruction-list): New function, exported by (system vm
  instruction).

* libguile/objcodes.c: Wire up the bits needed to detect the new RTL
  bytecode and load it, as appropriate.

19 files changed, 3624 insertions, 27 deletions

diff --git a/.gitignore b/.gitignore
index 90bacbe7d..b136c7ae2 100644
--- a/.gitignore
+++ b/.gitignore
@@ -156,3 +156,4 @@ INSTALL
 /test-suite/standalone/test-smob-mark
 /test-suite/standalone/test-scm-values
 /test-suite/standalone/test-scm-to-latin1-string
+/libguile/vm-operations.h
diff --git a/libguile/Makefile.am b/libguile/Makefile.am
index 7c7a34b44..ce437e41e 100644
--- a/libguile/Makefile.am
+++ b/libguile/Makefile.am
@@ -433,9 +433,18 @@ DOT_I_FILES = vm-i-system.i vm-i-scheme.i vm-i-loader.i
 .c.i:
 	$(AM_V_GEN)$(GREP) '^VM_DEFINE' $< > $@
 
+vm-operations.h: vm-engine.c
+	@echo '/* This file was generated automatically from $<; do not' > $@
+	@echo '   edit.  See the source file for copyright information.  */' >> $@
+	@echo '' >> $@
+	@echo "#define FOR_EACH_VM_OPERATION(M) \\" >> $@
+	$(AM_V_GEN)$(GREP) '^ *VM_DEFINE_OP' $< \
+	| sed -e 's,VM_DEFINE_OP (\(.*\)).*,  M (\1) \\,' >> $@
+	@echo '' >> $@
+
 BUILT_SOURCES = cpp-E.c cpp-SIG.c libpath.h \
     scmconfig.h \
-    $(DOT_I_FILES) $(DOT_X_FILES) $(EXTRA_DOT_X_FILES)
+    $(DOT_I_FILES) vm-operations.h $(DOT_X_FILES) $(EXTRA_DOT_X_FILES)
 
 # Force the generation of `guile-procedures.texi' because the top-level
 # Makefile expects it to be built.
diff --git a/libguile/evalext.c b/libguile/evalext.c
index 3e04a7a59..f955cee7f 100644
--- a/libguile/evalext.c
+++ b/libguile/evalext.c
@@ -1,4 +1,4 @@
-/* Copyright (C) 1998,1999,2000,2001,2002,2003, 2006, 2008, 2009, 2010, 2011 Free Software Foundation, Inc.
+/* Copyright (C) 1998,1999,2000,2001,2002,2003, 2006, 2008, 2009, 2010, 2011, 2012 Free Software Foundation, Inc.
  * 
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public License
@@ -87,6 +87,7 @@ SCM_DEFINE (scm_self_evaluating_p, "self-evaluating?", 1, 0, 0,
 	case scm_tc7_number:
 	case scm_tc7_string:
 	case scm_tc7_smob:
+	case scm_tc7_rtl_program:
 	case scm_tc7_program:
 	case scm_tc7_bytevector:
 	case scm_tc7_array:
diff --git a/libguile/frames.c b/libguile/frames.c
index 0338d18db..8ce5aa0b0 100644
--- a/libguile/frames.c
+++ b/libguile/frames.c
@@ -129,11 +129,21 @@ SCM_DEFINE (scm_frame_num_locals, "frame-num-locals", 1, 0, 0,
 	    "")
 #define FUNC_NAME s_scm_frame_num_locals
 {
-  SCM *sp, *p;
+  SCM *fp, *sp, *p;
   unsigned int n = 0;
 
   SCM_VALIDATE_VM_FRAME (1, frame);
 
+  fp = SCM_VM_FRAME_FP (frame);
+  sp = SCM_VM_FRAME_SP (frame);
+  p = SCM_FRAME_STACK_ADDRESS (SCM_VM_FRAME_FP (frame));
+
+  if (SCM_RTL_PROGRAM_P (fp[-1]))
+    /* The frame size of an RTL program is fixed, except in the case of
+       passing a wrong number of arguments to the program.  So we do
+       need to use an SP for determining the number of locals.  */
+    return scm_from_uint32 (sp + 1 - p);
+
   sp = SCM_VM_FRAME_SP (frame);
   p = SCM_FRAME_STACK_ADDRESS (SCM_VM_FRAME_FP (frame));
   while (p <= sp)
diff --git a/libguile/frames.h b/libguile/frames.h
index 71d5b124d..9105311f1 100644
--- a/libguile/frames.h
+++ b/libguile/frames.h
@@ -1,4 +1,4 @@
-/* Copyright (C) 2001, 2009, 2010, 2011 Free Software Foundation, Inc.
+/* Copyright (C) 2001, 2009, 2010, 2011, 2012 Free Software Foundation, Inc.
  * * 
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public License
@@ -100,6 +100,37 @@ struct scm_vm_frame
 
 
 /*
+ * RTL frames
+ */
+
+/* The frame format for the new RTL programs is almost like that for the
+   stack-vm programs.  They differ in their handling of MV returns,
+   however.  For RTL, every call is an MV call: every call has an MVRA.
+   Unlike the stack-vm programs, the MVRA for RTL programs is computable
+   from the RA -- it's always one word (4 bytes) before the RA.
+
+   Until we completely migrate to the RTL VM, we will also write the
+   MVRA to the stack.
+
+   When an RTL program returns multiple values, it will shuffle them
+   down to start contiguously from slot 0, as for a tail call.  This
+   means that when the caller goes to access them, there are 2 or 3
+   empty words between the top of the caller stack and the bottom of the
+   values, corresponding to the frame that was just popped.
+*/
+
+#define SCM_FRAME_RTL_RETURN_ADDRESS(fp)                \
+  ((scm_t_uint32 *) SCM_FRAME_RETURN_ADDRESS (fp))
+#define SCM_FRAME_SET_RTL_RETURN_ADDRESS(fp, ip)        \
+  SCM_FRAME_SET_RETURN_ADDRESS (fp, (scm_t_uint8 *) (ip))
+
+#define SCM_FRAME_RTL_MV_RETURN_ADDRESS(fp)             \
+  ((scm_t_uint32 *) SCM_FRAME_MV_RETURN_ADDRESS (fp))
+#define SCM_FRAME_SET_RTL_MV_RETURN_ADDRESS(fp, ip)     \
+  SCM_FRAME_SET_MV_RETURN_ADDRESS (fp, (scm_t_uint8 *) (ip))
+
+
+/*
  * Heap frames
  */
 
diff --git a/libguile/goops.c b/libguile/goops.c
index 355e5efa4..74ded73ff 100644
--- a/libguile/goops.c
+++ b/libguile/goops.c
@@ -301,6 +301,9 @@ SCM_DEFINE (scm_class_of, "class-of", 1, 0, 0,
 	  else
 	    return scm_class_procedure;
 
+	case scm_tc7_rtl_program:
+          return scm_class_procedure;
+
 	case scm_tc7_smob:
 	  {
 	    scm_t_bits type = SCM_TYP16 (x);
diff --git a/libguile/instructions.c b/libguile/instructions.c
index f3b8963d2..08f7cd60d 100644
--- a/libguile/instructions.c
+++ b/libguile/instructions.c
@@ -1,4 +1,4 @@
-/* Copyright (C) 2001, 2009, 2010, 2011 Free Software Foundation, Inc.
+/* Copyright (C) 2001, 2009, 2010, 2011, 2012, 2013 Free Software Foundation, Inc.
  * 
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public License
@@ -40,6 +40,83 @@ struct scm_instruction {
   SCM symname;                  /* filled in later */
 };
 
+
+#define OP_HAS_ARITY (1U << 0)
+
+#define FOR_EACH_INSTRUCTION_WORD_TYPE(M)       \
+    M(X32)                                      \
+    M(U8_X24)                                   \
+    M(U8_U24)                                   \
+    M(U8_L24)                                   \
+    M(U8_R24)                                   \
+    M(U8_U8_I16)                                \
+    M(U8_U8_U8_U8)                              \
+    M(U8_U12_U12)                               \
+    M(U32) /* Unsigned. */                      \
+    M(I32) /* Immediate. */                     \
+    M(A32) /* Immediate, high bits. */          \
+    M(B32) /* Immediate, low bits. */           \
+    M(N32) /* Non-immediate. */                 \
+    M(S32) /* Scheme value (indirected). */     \
+    M(L32) /* Label. */                         \
+    M(LO32) /* Label with offset. */            \
+    M(X8_U24)                                   \
+    M(X8_U12_U12)                               \
+    M(X8_R24)                                   \
+    M(X8_L24)                                   \
+    M(B1_X7_L24)                                \
+    M(B1_U7_L24)
+
+#define TYPE_WIDTH 5
+
+enum word_type
+  {
+#define ENUM(type) type,
+    FOR_EACH_INSTRUCTION_WORD_TYPE (ENUM)
+#undef ENUM
+  };
+
+static SCM word_type_symbols[] =
+  {
+#define FALSE(type) SCM_BOOL_F,
+    FOR_EACH_INSTRUCTION_WORD_TYPE (FALSE)
+#undef FALSE
+  };
+
+#define OP(n,type) ((type) << (n*TYPE_WIDTH))
+
+/* The VM_DEFINE_OP macro uses a CPP-based DSL to describe what kinds of
+   arguments each RTL instruction takes.  This piece of code is the only
+   bit that actually interprets that language.  These macro definitions
+   encode the operand types into bits in a 32-bit integer.
+
+   (rtl-instruction-list) parses those encoded values into lists of
+   symbols, one for each 32-bit word that the operator takes.  (system
+   vm rtl) uses those word types to generate assemblers and
+   disassemblers for the instructions.  */
+
+#define OP1(type0) \
+  (OP (0, type0))
+#define OP2(type0, type1) \
+  (OP (0, type0) | OP (1, type1))
+#define OP3(type0, type1, type2) \
+  (OP (0, type0) | OP (1, type1) | OP (2, type2))
+#define OP4(type0, type1, type2, type3) \
+  (OP (0, type0) | OP (1, type1) | OP (2, type2) | OP (3, type3))
+
+#define OP_DST (1 << (TYPE_WIDTH * 5))
+
+#define WORD_TYPE(n, word) \
+  (((word) >> ((n) * TYPE_WIDTH)) & ((1 << TYPE_WIDTH) - 1))
+
+struct scm_rtl_instruction {
+  enum scm_rtl_opcode opcode;	/* opcode */
+  const char *name;		/* instruction name */
+  scm_t_uint32 meta;
+  SCM symname;                  /* filled in later */
+};
+
+
 #define SCM_VALIDATE_LOOKUP_INSTRUCTION(pos, var, cvar)               \
   do {                                                                \
     cvar = scm_lookup_instruction_by_name (var);                      \
@@ -82,6 +159,37 @@ fetch_instruction_table ()
   return table;
 }
 
+static struct scm_rtl_instruction*
+fetch_rtl_instruction_table ()
+{
+  static struct scm_rtl_instruction *table = NULL;
+
+  scm_i_pthread_mutex_lock (&itable_lock);
+  if (SCM_UNLIKELY (!table))
+    {
+      size_t bytes = SCM_VM_NUM_INSTRUCTIONS * sizeof(struct scm_rtl_instruction);
+      int i;
+      table = malloc (bytes);
+      memset (table, 0, bytes);
+
+#define INIT(opcode, tag, name_, meta_) table[opcode].name = name_; table[opcode].meta = meta_;
+      FOR_EACH_VM_OPERATION (INIT);
+#undef INIT
+
+      for (i = 0; i < SCM_VM_NUM_INSTRUCTIONS; i++)
+        {
+          table[i].opcode = i;
+          if (table[i].name)
+            table[i].symname = scm_from_utf8_symbol (table[i].name);
+          else
+            table[i].symname = SCM_BOOL_F;
+        }
+    }
+  scm_i_pthread_mutex_unlock (&itable_lock);
+
+  return table;
+}
+
 static struct scm_instruction *
 scm_lookup_instruction_by_name (SCM name)
 {
@@ -127,6 +235,57 @@ SCM_DEFINE (scm_instruction_list, "instruction-list", 0, 0, 0,
 }
 #undef FUNC_NAME
 
+SCM_DEFINE (scm_rtl_instruction_list, "rtl-instruction-list", 0, 0, 0,
+	    (void),
+	    "")
+#define FUNC_NAME s_scm_rtl_instruction_list
+{
+  SCM list = SCM_EOL;
+  int i;
+  struct scm_rtl_instruction *ip = fetch_rtl_instruction_table ();
+  for (i = 0; i < SCM_VM_NUM_INSTRUCTIONS; i++)
+    if (ip[i].name)
+      {
+        scm_t_uint32 meta = ip[i].meta;
+        SCM tail = SCM_EOL;
+        int len;
+
+        /* Format: (name opcode len rest? out br in) */
+
+        if (WORD_TYPE (3, meta))
+          len = 4;
+        else if (WORD_TYPE (2, meta))
+          len = 3;
+        else if (WORD_TYPE (1, meta))
+          len = 2;
+        else if (WORD_TYPE (0, meta))
+          len = 1;
+        else
+          abort ();
+
+        switch (len)
+          {
+          case 4:
+            tail = scm_cons (word_type_symbols[WORD_TYPE (3, meta)], tail);
+          case 3:
+            tail = scm_cons (word_type_symbols[WORD_TYPE (2, meta)], tail);
+          case 2:
+            tail = scm_cons (word_type_symbols[WORD_TYPE (1, meta)], tail);
+          case 1:
+            tail = scm_cons (word_type_symbols[WORD_TYPE (0, meta)], tail);
+          default:
+            tail = scm_cons (scm_from_int (ip[i].opcode), tail);
+            tail = scm_cons (ip[i].symname, tail);
+            break;
+          }
+
+        list = scm_cons (tail, list);
+      }
+
+  return scm_reverse_x (list, SCM_EOL);
+}
+#undef FUNC_NAME
+
 SCM_DEFINE (scm_instruction_p, "instruction?", 1, 0, 0,
 	    (SCM obj),
 	    "")
@@ -208,6 +367,11 @@ scm_bootstrap_instructions (void)
                             "scm_init_instructions",
                             (scm_t_extension_init_func)scm_init_instructions,
                             NULL);
+
+#define INIT(type) \
+  word_type_symbols[type] = scm_from_utf8_symbol (#type);
+    FOR_EACH_INSTRUCTION_WORD_TYPE (INIT)
+#undef INIT
 }
 
 void
diff --git a/libguile/instructions.h b/libguile/instructions.h
index a2263228f..bf27afa6c 100644
--- a/libguile/instructions.h
+++ b/libguile/instructions.h
@@ -1,4 +1,4 @@
-/* Copyright (C) 2001, 2009 Free Software Foundation, Inc.
+/* Copyright (C) 2001, 2009, 2012 Free Software Foundation, Inc.
  * 
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public License
@@ -20,6 +20,59 @@
 #define _SCM_INSTRUCTIONS_H_
 
 #include <libguile.h>
+#include <libguile/vm-operations.h>
+
+enum scm_rtl_opcode
+  {
+#define ENUM(opcode, tag, name, meta) scm_rtl_op_##tag = opcode,
+    FOR_EACH_VM_OPERATION(ENUM)
+#undef ENUM
+  };
+
+#define SCM_PACK_RTL_8_8_8(op,a,b,c) ((op) | ((a) << 8) | ((b) << 16) | ((d) << 24))
+#define SCM_PACK_RTL_8_16(op,a,b) ((op) | ((a) << 8) | ((b) << 16))
+#define SCM_PACK_RTL_16_8(op,a,b) ((op) | ((a) << 16) | ((b) << 24))
+#define SCM_PACK_RTL_24(op,a) ((op) | ((a) << 8))
+
+#define SCM_UNPACK_RTL_8_8_8(op,a,b,c)    \
+  do                                      \
+    {                                     \
+      a = (op >> 8) & 0xff;               \
+      b = (op >> 16) & 0xff;              \
+      c = op >> 24;                       \
+    }                                     \
+  while (0)
+
+#define SCM_UNPACK_RTL_8_16(op,a,b)       \
+  do                                      \
+    {                                     \
+      a = (op >> 8) & 0xff;               \
+      b = op >> 16;                       \
+    }                                     \
+  while (0)
+
+#define SCM_UNPACK_RTL_16_8(op,a,b)       \
+  do                                      \
+    {                                     \
+      a = (op >> 8) & 0xffff;             \
+      b = op >> 24;                       \
+    }                                     \
+  while (0)
+
+#define SCM_UNPACK_RTL_12_12(op,a,b)      \
+  do                                      \
+    {                                     \
+      a = (op >> 8) & 0xfff;              \
+      b = op >> 20;                       \
+    }                                     \
+  while (0)
+
+#define SCM_UNPACK_RTL_24(op,a)           \
+  do                                      \
+    {                                     \
+      a = op >> 8;                        \
+    }                                     \
+  while (0)
 
 #define SCM_VM_NUM_INSTRUCTIONS (1<<8)
 #define SCM_VM_INSTRUCTION_MASK (SCM_VM_NUM_INSTRUCTIONS-1)
@@ -33,6 +86,8 @@ enum scm_opcode {
 #undef VM_INSTRUCTION_TO_OPCODE
 };
 
+SCM_INTERNAL SCM scm_rtl_instruction_list (void);
+
 SCM_API SCM scm_instruction_list (void);
 SCM_API SCM scm_instruction_p (SCM obj);
 SCM_API SCM scm_instruction_length (SCM inst);
diff --git a/libguile/objcodes.c b/libguile/objcodes.c
index 4daba55ab..734bddeb3 100644
--- a/libguile/objcodes.c
+++ b/libguile/objcodes.c
@@ -94,7 +94,8 @@ static void register_elf (char *data, size_t len);
 enum bytecode_kind
   {
     BYTECODE_KIND_NONE,
-    BYTECODE_KIND_GUILE_2_0
+    BYTECODE_KIND_GUILE_2_0,
+    BYTECODE_KIND_GUILE_2_2
   };
 
 static SCM
@@ -110,6 +111,10 @@ pointer_to_procedure (enum bytecode_kind bytecode_kind, char *ptr)
         objcode = scm_double_cell (tag, (scm_t_bits) ptr, SCM_BOOL_F_BITS, 0);
         return scm_make_program (objcode, SCM_BOOL_F, SCM_UNDEFINED);
       }
+    case BYTECODE_KIND_GUILE_2_2:
+      {
+        return scm_i_make_rtl_program ((scm_t_uint32 *) ptr);
+      }
     case BYTECODE_KIND_NONE:
     default:
       abort ();
@@ -302,29 +307,52 @@ process_dynamic_segment (char *base, Elf_Phdr *dyn_phdr,
           {
             scm_t_uint16 major = dyn[i].d_un.d_val >> 16;
             scm_t_uint16 minor = dyn[i].d_un.d_val & 0xffff;
-            if (major != 0x0200)
-              return "incompatible bytecode kind";
-            if (minor > SCM_OBJCODE_MINOR_VERSION)
-              return "incompatible bytecode version";
-            bytecode_kind = BYTECODE_KIND_GUILE_2_0;
+            switch (major)
+              {
+              case 0x0200:
+                bytecode_kind = BYTECODE_KIND_GUILE_2_0;
+                if (minor > SCM_OBJCODE_MINOR_VERSION)
+                  return "incompatible bytecode version";
+                break;
+              case 0x0202:
+                bytecode_kind = BYTECODE_KIND_GUILE_2_2;
+                if (minor)
+                  return "incompatible bytecode version";
+                break;
+              default:
+                return "incompatible bytecode kind";
+              }
             break;
           }
         }
     }
 
-  if (bytecode_kind != BYTECODE_KIND_GUILE_2_0)
-    return "missing DT_GUILE_RTL_VERSION";
-  if (init)
-    return "unexpected DT_INIT";
-  if ((scm_t_uintptr) entry % 8)
-    return "unaligned DT_GUILE_ENTRY";
   if (!entry)
     return "missing DT_GUILE_ENTRY";
 
+  switch (bytecode_kind)
+    {
+    case BYTECODE_KIND_GUILE_2_0:
+      if (init)
+        return "unexpected DT_INIT";
+      if ((scm_t_uintptr) entry % 8)
+        return "unaligned DT_GUILE_ENTRY";
+      break;
+    case BYTECODE_KIND_GUILE_2_2:
+      if ((scm_t_uintptr) init % 4)
+        return "unaligned DT_INIT";
+      if ((scm_t_uintptr) entry % 4)
+        return "unaligned DT_GUILE_ENTRY";
+      break;
+    case BYTECODE_KIND_NONE:
+    default:
+      return "missing DT_GUILE_RTL_VERSION";
+    }
+
   if (gc_root)
     GC_add_roots (gc_root, gc_root + gc_root_size);
 
-  *init_out = SCM_BOOL_F;
+  *init_out = init ? pointer_to_procedure (bytecode_kind, init) : SCM_BOOL_F;
   *entry_out = pointer_to_procedure (bytecode_kind, entry);
   return NULL;
 }
diff --git a/libguile/print.c b/libguile/print.c
index 652409134..f912a3586 100644
--- a/libguile/print.c
+++ b/libguile/print.c
@@ -656,6 +656,9 @@ iprin1 (SCM exp, SCM port, scm_print_state *pstate)
 	case scm_tc7_variable:
 	  scm_i_variable_print (exp, port, pstate);
 	  break;
+	case scm_tc7_rtl_program:
+	  scm_i_rtl_program_print (exp, port, pstate);
+	  break;
 	case scm_tc7_program:
 	  scm_i_program_print (exp, port, pstate);
 	  break;
diff --git a/libguile/procprop.c b/libguile/procprop.c
index ff4648d00..d37495b2b 100644
--- a/libguile/procprop.c
+++ b/libguile/procprop.c
@@ -82,6 +82,14 @@ scm_i_procedure_arity (SCM proc, int *req, int *opt, int *rest)
 
           return 1;
         }
+      else if (SCM_RTL_PROGRAM_P (proc))
+        {
+          *req = 0;
+          *opt = 0;
+          *rest = 1;
+
+          return 1;
+        }
       else
         return 0;
     }
diff --git a/libguile/procs.c b/libguile/procs.c
index 5899df035..bda6d3448 100644
--- a/libguile/procs.c
+++ b/libguile/procs.c
@@ -1,5 +1,5 @@
 /* Copyright (C) 1995, 1996, 1997, 1999, 2000, 2001, 2006, 2008, 2009,
- *   2010, 2011, 2012 Free Software Foundation, Inc.
+ *   2010, 2011, 2012, 2013 Free Software Foundation, Inc.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public License
@@ -48,6 +48,7 @@ SCM_DEFINE (scm_procedure_p, "procedure?", 1, 0, 0,
 #define FUNC_NAME s_scm_procedure_p
 {
   return scm_from_bool (SCM_PROGRAM_P (obj)
+                        || SCM_RTL_PROGRAM_P (obj)
                         || (SCM_STRUCTP (obj) && SCM_STRUCT_APPLICABLE_P (obj))
                         || (SCM_HAS_TYP7 (obj, scm_tc7_smob)
                             && SCM_SMOB_APPLICABLE_P (obj)));
diff --git a/libguile/programs.c b/libguile/programs.c
index 128e0312a..eb5972ab3 100644
--- a/libguile/programs.c
+++ b/libguile/programs.c
@@ -1,4 +1,4 @@
-/* Copyright (C) 2001, 2009, 2010, 2011 Free Software Foundation, Inc.
+/* Copyright (C) 2001, 2009, 2010, 2011, 2012, 2013 Free Software Foundation, Inc.
  * 
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public License
@@ -69,6 +69,58 @@ SCM_DEFINE (scm_make_program, "make-program", 1, 2, 0,
 }
 #undef FUNC_NAME
 
+SCM_DEFINE (scm_make_rtl_program, "make-rtl-program", 1, 2, 0,
+	    (SCM bytevector, SCM byte_offset, SCM free_variables),
+	    "")
+#define FUNC_NAME s_scm_make_rtl_program
+{
+  scm_t_uint8 *code;
+  scm_t_uint32 offset;
+
+  if (!scm_is_bytevector (bytevector))
+    scm_wrong_type_arg (FUNC_NAME, 1, bytevector);
+  if (SCM_UNBNDP (byte_offset))
+    offset = 0;
+  else
+    {
+      offset = scm_to_uint32 (byte_offset);
+      if (offset > SCM_BYTEVECTOR_LENGTH (bytevector))
+        SCM_OUT_OF_RANGE (2, byte_offset);
+    }
+
+  code = (scm_t_uint8*) SCM_BYTEVECTOR_CONTENTS (bytevector) + offset;
+  if (((scm_t_uintptr) code) % 4)
+    SCM_OUT_OF_RANGE (2, byte_offset);
+
+  if (SCM_UNBNDP (free_variables) || scm_is_false (free_variables))
+    return scm_cell (scm_tc7_rtl_program, (scm_t_bits) code);
+  else
+    abort ();
+}
+#undef FUNC_NAME
+
+SCM_DEFINE (scm_rtl_program_code, "rtl-program-code", 1, 0, 0,
+            (SCM program),
+            "")
+#define FUNC_NAME s_scm_rtl_program_code
+{
+  SCM_VALIDATE_RTL_PROGRAM (1, program);
+
+  /* FIXME: we need scm_from_uintptr ().  */
+  return scm_from_size_t ((size_t) SCM_RTL_PROGRAM_CODE (program));
+}
+#undef FUNC_NAME
+
+void
+scm_i_rtl_program_print (SCM program, SCM port, scm_print_state *pstate)
+{
+  scm_puts_unlocked ("#<rtl-program ", port);
+  scm_uintprint (SCM_UNPACK (program), 16, port);
+  scm_putc_unlocked (' ', port);
+  scm_uintprint ((scm_t_uintptr) SCM_RTL_PROGRAM_CODE (program), 16, port);
+  scm_putc_unlocked ('>', port);
+}
+
 void
 scm_i_program_print (SCM program, SCM port, scm_print_state *pstate)
 {
@@ -121,6 +173,15 @@ SCM_DEFINE (scm_program_p, "program?", 1, 0, 0,
 }
 #undef FUNC_NAME
 
+SCM_DEFINE (scm_rtl_program_p, "rtl-program?", 1, 0, 0,
+	    (SCM obj),
+	    "")
+#define FUNC_NAME s_scm_rtl_program_p
+{
+  return scm_from_bool (SCM_RTL_PROGRAM_P (obj));
+}
+#undef FUNC_NAME
+
 SCM_DEFINE (scm_program_base, "program-base", 1, 0, 0,
 	    (SCM program),
 	    "")
diff --git a/libguile/programs.h b/libguile/programs.h
index d53fd8f84..732594cd2 100644
--- a/libguile/programs.h
+++ b/libguile/programs.h
@@ -1,4 +1,4 @@
-/* Copyright (C) 2001, 2009, 2010, 2011 Free Software Foundation, Inc.
+/* Copyright (C) 2001, 2009, 2010, 2011, 2012, 2013 Free Software Foundation, Inc.
  * 
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public License
@@ -23,6 +23,31 @@
 #include <libguile/objcodes.h>
 
 /*
+ * The new RTL programs.
+ */
+
+#define SCM_RTL_PROGRAM_P(x) (SCM_HAS_TYP7 (x, scm_tc7_rtl_program))
+#define SCM_RTL_PROGRAM_CODE(x) ((scm_t_uint32 *) SCM_CELL_WORD_1 (x))
+#define SCM_RTL_PROGRAM_FREE_VARIABLES(x) (SCM_CELL_OBJECT_LOC (x, 2))
+#define SCM_RTL_PROGRAM_FREE_VARIABLE_REF(x,i) (SCM_RTL_PROGRAM_FREE_VARIABLES (x)[i])
+#define SCM_RTL_PROGRAM_FREE_VARIABLE_SET(x,i,v) (SCM_RTL_PROGRAM_FREE_VARIABLES (x)[i]=(v))
+#define SCM_RTL_PROGRAM_NUM_FREE_VARIABLES(x) (SCM_CELL_WORD_0 (x) >> 16)
+#define SCM_VALIDATE_RTL_PROGRAM(p,x) SCM_MAKE_VALIDATE (p, x, RTL_PROGRAM_P)
+
+static inline SCM
+scm_i_make_rtl_program (const scm_t_uint32 *code)
+{
+  return scm_cell (scm_tc7_rtl_program, (scm_t_bits)code);
+}
+
+SCM_INTERNAL SCM scm_make_rtl_program (SCM bytevector, SCM byte_offset, SCM free_variables);
+SCM_INTERNAL SCM scm_rtl_program_p (SCM obj);
+SCM_INTERNAL SCM scm_rtl_program_code (SCM program);
+
+SCM_INTERNAL void scm_i_rtl_program_print (SCM program, SCM port,
+                                           scm_print_state *pstate);
+
+/*
  * Programs
  */
 
diff --git a/libguile/tags.h b/libguile/tags.h
index a194ea0be..fcfc01478 100644
--- a/libguile/tags.h
+++ b/libguile/tags.h
@@ -425,7 +425,7 @@ typedef union SCM { struct { scm_t_bits n; } n; } SCM;
 
 #define scm_tc7_unused_17	61
 #define scm_tc7_unused_21	63
-#define scm_tc7_unused_19	69
+#define scm_tc7_rtl_program	69
 #define scm_tc7_program		79
 #define scm_tc7_weak_set	85
 #define scm_tc7_weak_table	87
diff --git a/libguile/vm-engine.c b/libguile/vm-engine.c
index 44546323b..d0708233b 100644
--- a/libguile/vm-engine.c
+++ b/libguile/vm-engine.c
@@ -16,7 +16,34 @@
  * 02110-1301 USA
  */
 
-/* This file is included in vm.c multiple times */
+/* This file is included in vm.c multiple times.  */
+
+
+/* Virtual Machine
+
+   This file contains two virtual machines.  First, the old one -- the
+   one that is currently used, and corresponds to Guile 2.0.  It's a
+   stack machine, meaning that most instructions pop their operands from
+   the top of the stack, and push results there too.
+
+   Following it is the new virtual machine.  It's a register machine,
+   meaning that intructions address their operands by index, and store
+   results in indexed slots as well.  Those slots are on the stack.
+   It's somewhat confusing to call it a register machine, given that the
+   values are on the stack.  Perhaps it needs a new name.
+
+   Anyway, things are in a transitional state.  We're going to try to
+   avoid munging the old VM very much while we flesh out the new one.
+   We're also going to try to make them interoperable, as much as
+   possible -- to have the old VM be able to call procedures for the new
+   VM, and vice versa.  This should ease the bootstrapping process.  */
+
+
+/* The old VM.  */
+static SCM VM_NAME (SCM, SCM, SCM*, int);
+/* The new VM.  */
+static SCM RTL_VM_NAME (SCM, SCM, SCM*, size_t);
+
 
 #if (VM_ENGINE == SCM_VM_REGULAR_ENGINE)
 # define VM_USE_HOOKS		0	/* Various hooks */
@@ -379,6 +406,29 @@ VM_NAME (SCM vm, SCM program, SCM *argv, int nargs)
     {
       if (SCM_STRUCTP (program) && SCM_STRUCT_APPLICABLE_P (program))
         fp[-1] = SCM_STRUCT_PROCEDURE (program);
+      else if (SCM_HAS_TYP7 (program, scm_tc7_rtl_program))
+        {
+          SCM ret;
+          SYNC_ALL ();
+
+          ret = RTL_VM_NAME (vm, program, fp, sp - fp + 1);
+
+          NULLSTACK_FOR_NONLOCAL_EXIT ();
+
+          if (SCM_UNLIKELY (SCM_VALUESP (ret)))
+            {
+              /* multiple values returned to continuation */
+              ret = scm_struct_ref (ret, SCM_INUM0);
+              nvalues = scm_ilength (ret);
+              PUSH_LIST (ret, scm_is_null);
+              goto vm_return_values;
+            }
+          else
+            {
+              PUSH (ret);
+              goto vm_return;
+            }
+        }
       else if (SCM_HAS_TYP7 (program, scm_tc7_smob)
                && SCM_SMOB_APPLICABLE_P (program))
         {
@@ -450,8 +500,3102 @@ VM_NAME (SCM vm, SCM program, SCM *argv, int nargs)
 #undef RETURN
 #undef RETURN_ONE_VALUE
 #undef RETURN_VALUE_LIST
+#undef SYNC_ALL
+#undef SYNC_BEFORE_GC
+#undef SYNC_IP
+#undef SYNC_REGISTER
+#undef VARIABLE_BOUNDP
+#undef VARIABLE_REF
+#undef VARIABLE_SET
+#undef VM_DEFINE_OP
+#undef VM_INSTRUCTION_TO_LABEL
+
+
+
+
+/* Virtual Machine
+
+   This is Guile's new virtual machine.  When I say "new", I mean
+   relative to the current virtual machine.  At some point it will
+   become "the" virtual machine, and we'll delete this paragraph.  As
+   such, the rest of the comments speak as if there's only one VM.
+
+   <more overview here>
+ */
+
+
+/* The VM has three state bits: the instruction pointer (IP), the frame
+   pointer (FP), and the top-of-stack pointer (SP).  We cache the first
+   two of these in machine registers, local to the VM, because they are
+   used extensively by the VM.  As the SP is used more by code outside
+   the VM than by the VM itself, we don't bother caching it locally.
+
+   Since the FP changes infrequently, relative to the IP, we keep vp->fp
+   in sync with the local FP.  This would be a big lose for the IP,
+   though, so instead of updating vp->ip all the time, we call SYNC_IP
+   whenever we would need to know the IP of the top frame.  In practice,
+   we need to SYNC_IP whenever we call out of the VM to a function that
+   would like to walk the stack, perhaps as the result of an
+   exception.  */
+
+#define SYNC_IP() \
+  vp->ip = (scm_t_uint8 *) (ip)
+
+#define SYNC_REGISTER() \
+  SYNC_IP()
+#define SYNC_BEFORE_GC() /* Only SP and FP needed to trace GC */
+#define SYNC_ALL() /* FP already saved */ \
+  SYNC_IP()
+
+#define CHECK_OVERFLOW(sp)                      \
+  do {                                          \
+    if (SCM_UNLIKELY ((sp) >= stack_limit))     \
+      vm_error_stack_overflow (vp);             \
+  } while (0)
+
+/* Reserve stack space for a frame.  Will check that there is sufficient
+   stack space for N locals, not including the procedure, in addition to
+   4 words to set up the next frame.  Invoke after preparing the new
+   frame and setting the fp and ip.  */
+#define ALLOC_FRAME(n)                                              \
+  do {                                                              \
+    SCM *new_sp = vp->sp = fp - 1 + n;                              \
+    CHECK_OVERFLOW (new_sp + 4);                                    \
+  } while (0)
+
+/* Reset the current frame to hold N locals.  Used when we know that no
+   stack expansion is needed.  */
+#define RESET_FRAME(n)                                              \
+  do {                                                              \
+    vp->sp = fp - 1 + n;                                            \
+  } while (0)
+
+/* Compute the number of locals in the frame.  This is equal to the
+   number of actual arguments when a function is first called.  */
+#define FRAME_LOCALS_COUNT()                                        \
+  (vp->sp + 1 - fp)
+
+/* Restore registers after returning from a frame.  */
+#define RESTORE_FRAME()                                             \
+  do {                                                              \
+  } while (0)
+
+
+#define CACHE_REGISTER()                        \
+  do {                                          \
+    ip = (scm_t_uint32 *) vp->ip;               \
+    fp = vp->fp;                                \
+  } while (0)
+
+#ifdef HAVE_LABELS_AS_VALUES
+# define BEGIN_DISPATCH_SWITCH /* */
+# define END_DISPATCH_SWITCH /* */
+# define NEXT(n)                                \
+  do                                            \
+    {                                           \
+      ip += n;                                  \
+      NEXT_HOOK ();                             \
+      op = *ip;                                 \
+      goto *jump_table[op & 0xff];              \
+    }                                           \
+  while (0)
+# define VM_DEFINE_OP(opcode, tag, name, meta)  \
+  op_##tag:
+#else
+# define BEGIN_DISPATCH_SWITCH                  \
+  vm_start:                                     \
+    NEXT_HOOK ();                               \
+    op = *ip;                                   \
+  switch (op & 0xff)                            \
+    {
+# define END_DISPATCH_SWITCH                    \
+  default:                                      \
+    goto vm_error_bad_instruction;              \
+    }
+# define NEXT(n)                                \
+  do                                            \
+    {                                           \
+      ip += n;                                  \
+      goto vm_start;                            \
+    }                                           \
+  while (0)
+# define VM_DEFINE_OP(opcode, tag, name, meta)  \
+  op_##tag:                                     \
+  case opcode:
+#endif
+
+#define LOCAL_REF(i)		SCM_FRAME_VARIABLE (fp, i)
+#define LOCAL_SET(i,o)		SCM_FRAME_VARIABLE (fp, i) = o
+
+#define VARIABLE_REF(v)		SCM_VARIABLE_REF (v)
+#define VARIABLE_SET(v,o)	SCM_VARIABLE_SET (v, o)
+#define VARIABLE_BOUNDP(v)      (!scm_is_eq (VARIABLE_REF (v), SCM_UNDEFINED))
+#define FREE_VARIABLE_REF(i)	SCM_RTL_PROGRAM_FREE_VARIABLE_REF (SCM_FRAME_PROGRAM (fp), i)
+
+#define RETURN_ONE_VALUE(ret)                           \
+  do {                                                  \
+    SCM val = ret;                                      \
+    SCM *sp = SCM_FRAME_LOWER_ADDRESS (fp);             \
+    VM_HANDLE_INTERRUPTS;                               \
+    ip = SCM_FRAME_RTL_RETURN_ADDRESS (fp);             \
+    vp->sp = sp;                                        \
+    fp = vp->fp = SCM_FRAME_DYNAMIC_LINK (fp);          \
+    *sp = val;                                          \
+    POP_CONTINUATION_HOOK (sp, 1);                      \
+    NEXT (0);                                           \
+  } while (0)
+
+/* While we could generate the list-unrolling code here, it's fine for
+   now to just tail-call (apply values vals).  */
+#define RETURN_VALUE_LIST(vals_)                        \
+  do {                                                  \
+    SCM vals = vals_;                                   \
+    VM_HANDLE_INTERRUPTS;                               \
+    fp[-1] = rtl_apply;                                 \
+    fp[0] = rtl_values;                                 \
+    fp[1] = vals;                                       \
+    RESET_FRAME (2);                                    \
+    ip = (scm_t_uint32 *) rtl_apply_code;               \
+    goto op_apply;                                      \
+  } while (0)
+
+#define BR_NARGS(rel)                           \
+  scm_t_uint16 expected;                        \
+  SCM_UNPACK_RTL_24 (op, expected);             \
+  if (FRAME_LOCALS_COUNT() rel expected)        \
+    {                                           \
+      scm_t_int32 offset = ip[1];               \
+      offset >>= 8; /* Sign-extending shift. */ \
+      NEXT (offset);                            \
+    }                                           \
+  NEXT (2)
+
+#define BR_UNARY(x, exp)                        \
+  scm_t_uint32 test;                            \
+  SCM x;                                        \
+  SCM_UNPACK_RTL_24 (op, test);                 \
+  x = LOCAL_REF (test);                         \
+  if ((ip[1] & 0x1) ? !(exp) : (exp))           \
+    {                                           \
+      scm_t_int32 offset = ip[1];               \
+      offset >>= 8; /* Sign-extending shift. */ \
+      if (offset < 0)                           \
+        VM_HANDLE_INTERRUPTS;                   \
+      NEXT (offset);                            \
+    }                                           \
+  NEXT (2)
+
+#define BR_BINARY(x, y, exp)                    \
+  scm_t_uint16 a, b;                            \
+  SCM x, y;                                     \
+  SCM_UNPACK_RTL_12_12 (op, a, b);              \
+  x = LOCAL_REF (a);                            \
+  y = LOCAL_REF (b);                            \
+  if ((ip[1] & 0x1) ? !(exp) : (exp))           \
+    {                                           \
+      scm_t_int32 offset = ip[1];               \
+      offset >>= 8; /* Sign-extending shift. */ \
+      if (offset < 0)                           \
+        VM_HANDLE_INTERRUPTS;                   \
+      NEXT (offset);                            \
+    }                                           \
+  NEXT (2)
+
+#define BR_ARITHMETIC(crel,srel)                                        \
+  {                                                                     \
+    scm_t_uint16 a, b;                                                  \
+    SCM x, y;                                                           \
+    SCM_UNPACK_RTL_12_12 (op, a, b);                                    \
+    x = LOCAL_REF (a);                                                  \
+    y = LOCAL_REF (b);                                                  \
+    if (SCM_I_INUMP (x) && SCM_I_INUMP (y))                             \
+      {                                                                 \
+        scm_t_signed_bits x_bits = SCM_UNPACK (x);                      \
+        scm_t_signed_bits y_bits = SCM_UNPACK (y);                      \
+        if (x_bits crel y_bits)                                         \
+          {                                                             \
+            scm_t_int32 offset = ip[1];                                 \
+            offset >>= 8; /* Sign-extending shift. */                   \
+            if (offset < 0)                                             \
+              VM_HANDLE_INTERRUPTS;                                     \
+            NEXT (offset);                                              \
+          }                                                             \
+        NEXT (2);                                                       \
+      }                                                                 \
+    else                                                                \
+      {                                                                 \
+        SYNC_IP ();                                                     \
+        if (scm_is_true (srel (x, y)))                                  \
+          {                                                             \
+            scm_t_int32 offset = ip[1];                                 \
+            offset >>= 8; /* Sign-extending shift. */                   \
+            if (offset < 0)                                             \
+              VM_HANDLE_INTERRUPTS;                                     \
+            NEXT (offset);                                              \
+          }                                                             \
+        NEXT (2);                                                       \
+      }                                                                 \
+  }
+
+#define ARGS1(a1)                               \
+  scm_t_uint16 dst, src;                        \
+  SCM a1;                                       \
+  SCM_UNPACK_RTL_12_12 (op, dst, src);          \
+  a1 = LOCAL_REF (src)
+#define ARGS2(a1, a2)                           \
+  scm_t_uint8 dst, src1, src2;                  \
+  SCM a1, a2;                                   \
+  SCM_UNPACK_RTL_8_8_8 (op, dst, src1, src2);   \
+  a1 = LOCAL_REF (src1);                        \
+  a2 = LOCAL_REF (src2)
+#define RETURN(x)                               \
+  do { LOCAL_SET (dst, x); NEXT (1); } while (0)
+
+/* The maximum/minimum tagged integers.  */
+#define INUM_MAX (INTPTR_MAX - 1)
+#define INUM_MIN (INTPTR_MIN + scm_tc2_int)
+
+#define BINARY_INTEGER_OP(CFUNC,SFUNC)                                      \
+  {                                                             \
+    ARGS2 (x, y);						\
+    if (SCM_I_INUMP (x) && SCM_I_INUMP (y))                     \
+      {                                                         \
+        scm_t_int64 n = SCM_I_INUM (x) CFUNC SCM_I_INUM (y);    \
+        if (SCM_FIXABLE (n))                                    \
+          RETURN (SCM_I_MAKINUM (n));                           \
+      }                                                         \
+    SYNC_IP ();                                                 \
+    RETURN (SFUNC (x, y));                                      \
+  }
+
+#define VM_VALIDATE_PAIR(x, proc)		\
+  VM_ASSERT (scm_is_pair (x), vm_error_not_a_pair (proc, x))
+  
+#define VM_VALIDATE_STRUCT(obj, proc)           \
+  VM_ASSERT (SCM_STRUCTP (obj), vm_error_not_a_pair (proc, obj))
+
+#define VM_VALIDATE_BYTEVECTOR(x, proc)		\
+  VM_ASSERT (SCM_BYTEVECTOR_P (x), vm_error_not_a_bytevector (proc, x))
+
+/* Return true (non-zero) if PTR has suitable alignment for TYPE.  */
+#define ALIGNED_P(ptr, type)			\
+  ((scm_t_uintptr) (ptr) % alignof_type (type) == 0)
+
+static SCM
+RTL_VM_NAME (SCM vm, SCM program, SCM *argv, size_t nargs_)
+{
+  /* Instruction pointer: A pointer to the opcode that is currently
+     running.  */
+  register scm_t_uint32 *ip IP_REG;
+
+  /* Frame pointer: A pointer into the stack, off of which we index
+     arguments and local variables.  Pushed at function calls, popped on
+     returns.  */
+  register SCM *fp FP_REG;
+
+  /* Current opcode: A cache of *ip.  */
+  register scm_t_uint32 op;
+
+  /* Cached variables. */
+  struct scm_vm *vp = SCM_VM_DATA (vm);
+  SCM *stack_limit = vp->stack_limit;	/* stack limit address */
+  scm_i_thread *current_thread = SCM_I_CURRENT_THREAD;
+  scm_i_jmp_buf registers;              /* used for prompts */
+
+#ifdef HAVE_LABELS_AS_VALUES
+  static const void **jump_table_pointer = NULL;
+  register const void **jump_table JT_REG;
+
+  if (SCM_UNLIKELY (!jump_table_pointer))
+    {
+      int i;
+      jump_table_pointer = malloc (SCM_VM_NUM_INSTRUCTIONS * sizeof (void*));
+      for (i = 0; i < SCM_VM_NUM_INSTRUCTIONS; i++)
+        jump_table_pointer[i] = &&vm_error_bad_instruction;
+#define INIT(opcode, tag, name, meta) jump_table_pointer[opcode] = &&op_##tag;
+      FOR_EACH_VM_OPERATION(INIT);
+#undef INIT
+    }
+
+  /* Attempt to keep JUMP_TABLE_POINTER in a register.  This saves one
+     load instruction at each instruction dispatch.  */
+  jump_table = jump_table_pointer;
+#endif
+
+  if (SCM_I_SETJMP (registers))
+    {
+      /* Non-local return.  The values are on the stack, on a new frame
+         set up to call `values' to return the values to the handler.
+         Cache the VM registers back from the vp, and dispatch to the
+         body of `values'.
+
+         Note, at this point, we must assume that any variable local to
+         vm_engine that can be assigned *has* been assigned. So we need
+         to pull all our state back from the ip/fp/sp.
+      */
+      CACHE_REGISTER ();
+      ABORT_CONTINUATION_HOOK (fp, FRAME_LOCALS_COUNT());
+      NEXT (0);
+    }
+
+  /* Load previous VM registers. */
+  CACHE_REGISTER ();
+
+  VM_HANDLE_INTERRUPTS;
+
+  /* Initialization */
+  {
+    SCM *base;
+
+    /* Check that we have enough space: 4 words for the boot
+       continuation, 4 + nargs for the procedure application, and 4 for
+       setting up a new frame.  */
+    base = vp->sp + 1;
+    CHECK_OVERFLOW (vp->sp + 4 + 4 + nargs_ + 4);
+
+    /* Since it's possible to receive the arguments on the stack itself,
+       and indeed the regular VM invokes us that way, shuffle up the
+       arguments first.  */
+    {
+      int i;
+      for (i = nargs_ - 1; i >= 0; i--)
+        base[8 + i] = argv[i];
+    }
+
+    /* Initial frame, saving previous fp and ip, with the boot
+       continuation.  */
+    base[0] = SCM_PACK (fp); /* dynamic link */
+    base[1] = SCM_PACK (0); /* the boot continuation does not return to scheme */
+    base[2] = SCM_PACK (ip); /* ra */
+    base[3] = rtl_boot_continuation;
+    fp = &base[4];
+    ip = rtl_boot_single_value_continuation_code;
+    if (ip - 1 != rtl_boot_multiple_value_continuation_code)
+      abort();
+
+    /* MV-call frame, function & arguments */
+    base[4] = SCM_PACK (fp); /* dynamic link */
+    base[5] = SCM_PACK (ip - 1); /* in RTL programs, MVRA precedes RA by one */
+    base[6] = SCM_PACK (ip); /* ra */
+    base[7] = program;
+    fp = vp->fp = &base[8];
+    RESET_FRAME (nargs_);
+  }
+
+ apply:
+  while (!SCM_RTL_PROGRAM_P (SCM_FRAME_PROGRAM (fp)))
+    {
+#if 0
+      SCM proc = SCM_FRAME_PROGRAM (fp);
+
+      if (SCM_STRUCTP (proc) && SCM_STRUCT_APPLICABLE_P (proc))
+        {
+          fp[-1] = SCM_STRUCT_PROCEDURE (proc);
+          continue;
+        }
+      if (SCM_HAS_TYP7 (proc, scm_tc7_smob) && SCM_SMOB_APPLICABLE_P (proc))
+        {
+          scm_t_uint32 n = FRAME_LOCALS_COUNT();
+
+          /* Shuffle args up, place smob in local 0. */
+          CHECK_OVERFLOW (vp->sp + 1);
+          vp->sp++;
+          while (n--)
+            LOCAL_SET (n + 1, LOCAL_REF (n));
+          LOCAL_SET (0, proc);
+
+          fp[-1] = SCM_SMOB_DESCRIPTOR (proc).apply_trampoline;
+          continue;
+        }
+
+      SYNC_IP();
+      vm_error_wrong_type_apply (proc);
+#else
+      SCM ret;
+      SYNC_ALL ();
+
+      ret = VM_NAME (vm, fp[-1], fp, FRAME_LOCALS_COUNT ());
+
+      if (SCM_UNLIKELY (SCM_VALUESP (ret)))
+        RETURN_VALUE_LIST (scm_struct_ref (ret, SCM_INUM0));
+      else
+        RETURN_ONE_VALUE (ret);
+#endif
+    }
+
+  /* Let's go! */
+  ip = SCM_RTL_PROGRAM_CODE (SCM_FRAME_PROGRAM (fp));
+  NEXT (0);
+
+  BEGIN_DISPATCH_SWITCH;
+  
+
+  
+
+  /*
+   * Call and return
+   */
+
+  /* halt _:24
+   *
+   * Bring the VM to a halt, returning the single value from r0.
+   */
+  VM_DEFINE_OP (0, halt, "halt", OP1 (U8_X24))
+    {
+      SCM ret = LOCAL_REF (0);
+
+      vp->ip = SCM_FRAME_RETURN_ADDRESS (fp);
+      vp->sp = SCM_FRAME_LOWER_ADDRESS (fp) - 1;
+      vp->fp = SCM_FRAME_DYNAMIC_LINK (fp);
+
+      return ret;
+    }
+
+  /* halt/values _:24
+   *
+   * Bring the VM to a halt, returning all the values on the stack.
+   */
+  VM_DEFINE_OP (1, halt_values, "halt/values", OP1 (U8_X24))
+    {
+      scm_t_ptrdiff n;
+      SCM *base;
+      SCM ret = SCM_EOL;
+
+      SYNC_BEFORE_GC();
+
+      base = fp + 4;
+      n = FRAME_LOCALS_COUNT ();
+      while (n--)
+        ret = scm_cons (base[n], ret);
+
+      vp->ip = SCM_FRAME_RETURN_ADDRESS (fp);
+      vp->sp = SCM_FRAME_LOWER_ADDRESS (fp) - 1;
+      vp->fp = SCM_FRAME_DYNAMIC_LINK (fp);
+
+      return scm_values (ret);
+    }
+
+  /* call from:24 _:8 proc:24 _:8 nargs:24 arg0:24 0:8 ...
+   *
+   * Call a procedure.  Push a call frame on at FROM, saving the return
+   * address and the fp.  Parse out NARGS, and push the procedure and
+   * arguments.  All arguments except for RETURN-LOC are 24-bit values.
+   * FROM, PROC, and NARGS are in the upper 24 bits of the words.  The
+   * ARGN... are in the lower 24 bits, with the upper 8 bits being 0.
+   *
+   * The MVRA of the new frame is set to point to the next instruction
+   * after the end of the `call' instruction.  The word following that
+   * is the RA.
+   */
+  VM_DEFINE_OP (2, call, "call", OP3 (U8_U24, X8_U24, X8_R24))
+    {
+      scm_t_uint32 from, proc, nargs, n;
+      SCM *old_fp = fp;
+
+      SCM_UNPACK_RTL_24 (op, from);
+      SCM_UNPACK_RTL_24 (ip[1], proc);
+      SCM_UNPACK_RTL_24 (ip[2], nargs);
+
+      VM_HANDLE_INTERRUPTS;
+
+      fp = vp->fp = old_fp + from + 4;
+      SCM_FRAME_SET_DYNAMIC_LINK (fp, old_fp);
+      SCM_FRAME_SET_RTL_MV_RETURN_ADDRESS (fp, ip + 3 + nargs);
+      SCM_FRAME_SET_RTL_RETURN_ADDRESS (fp, ip + 4 + nargs);
+      fp[-1] = old_fp[proc];
+      ALLOC_FRAME (nargs);
+
+      for (n = 0; n < nargs; n++)
+        LOCAL_SET (n, old_fp[ip[3 + n]]);
+
+      PUSH_CONTINUATION_HOOK ();
+      APPLY_HOOK ();
+
+      if (SCM_UNLIKELY (!SCM_RTL_PROGRAM_P (SCM_FRAME_PROGRAM (fp))))
+        goto apply;
+
+      ip = SCM_RTL_PROGRAM_CODE (SCM_FRAME_PROGRAM (fp));
+      NEXT (0);
+    }
+
+  /* call/values from:24 _:8 proc:24
+   *
+   * Call a procedure, with the values already pushed above a call frame
+   * at FROM.  This instruction is used to handle MV returns in the case
+   * that we can't inline the handler.
+   *
+   * As with `call', the next instruction after the call/values will be
+   * the MVRA, and the word after that instruction is the RA.
+   */
+  VM_DEFINE_OP (3, call_values, "call/values", OP2 (U8_U24, X8_U24))
+    {
+      scm_t_uint32 from, proc;
+      SCM *old_fp = fp;
+
+      SCM_UNPACK_RTL_24 (op, from);
+      SCM_UNPACK_RTL_24 (ip[1], proc);
+
+      VM_HANDLE_INTERRUPTS;
+
+      fp = vp->fp = old_fp + from + 4;
+      SCM_FRAME_SET_DYNAMIC_LINK (fp, old_fp);
+      SCM_FRAME_SET_RTL_MV_RETURN_ADDRESS (fp, ip + 2);
+      SCM_FRAME_SET_RTL_RETURN_ADDRESS (fp, ip + 3);
+      fp[-1] = old_fp[proc];
+
+      PUSH_CONTINUATION_HOOK ();
+      APPLY_HOOK ();
+
+      if (SCM_UNLIKELY (!SCM_RTL_PROGRAM_P (SCM_FRAME_PROGRAM (fp))))
+        goto apply;
+
+      ip = SCM_RTL_PROGRAM_CODE (SCM_FRAME_PROGRAM (fp));
+      NEXT (0);
+    }
+
+  /* tail-call nargs:24 _:8 proc:24
+   *
+   * Tail-call a procedure.  Requires that all of the arguments have
+   * already been shuffled into position.
+   */
+  VM_DEFINE_OP (4, tail_call, "tail-call", OP2 (U8_U24, X8_U24))
+    {
+      scm_t_uint32 nargs, proc;
+
+      SCM_UNPACK_RTL_24 (op, nargs);
+      SCM_UNPACK_RTL_24 (ip[1], proc);
+
+      VM_HANDLE_INTERRUPTS;
+
+      fp[-1] = LOCAL_REF (proc);
+      /* No need to check for overflow, as the compiler has already
+         ensured that this frame has enough space.  */
+      RESET_FRAME (nargs);
+
+      APPLY_HOOK ();
+
+      if (SCM_UNLIKELY (!SCM_RTL_PROGRAM_P (SCM_FRAME_PROGRAM (fp))))
+        goto apply;
+
+      ip = SCM_RTL_PROGRAM_CODE (SCM_FRAME_PROGRAM (fp));
+      NEXT (0);
+    }
+
+  /* return src:24
+   *
+   * Return a value.
+   */
+  VM_DEFINE_OP (5, return, "return", OP1 (U8_U24))
+    {
+      scm_t_uint32 src;
+      SCM_UNPACK_RTL_24 (op, src);
+      RETURN_ONE_VALUE (LOCAL_REF (src));
+    }
+
+  /* return-values nvalues:24
+   *
+   * Return a number of values from a call frame.  This opcode
+   * corresponds to an application of `values' in tail position.  As
+   * with tail calls, we expect that the NVALUES values have already
+   * been shuffled down to a contiguous array starting at slot 0.
+   */
+  VM_DEFINE_OP (6, return_values, "return/values", OP1 (U8_U24))
+    {
+      scm_t_uint32 nargs;
+      SCM_UNPACK_RTL_24 (op, nargs);
+      RESET_FRAME (nargs);
+      fp[-1] = rtl_values;
+      goto op_values;
+    }
+
+
+  
+
+  /*
+   * Specialized call stubs
+   */
+
+  /* subr-call ptr-idx:24
+   *
+   * Call a subr, passing all locals in this frame as arguments.  Fetch
+   * the foreign pointer from PTR-IDX, a free variable.  Return from the
+   * calling frame.  This instruction is part of the trampolines
+   * created in gsubr.c, and is not generated by the compiler.
+   */
+  VM_DEFINE_OP (7, subr_call, "subr-call", OP1 (U8_U24))
+    {
+      scm_t_uint32 ptr_idx;
+      SCM pointer, ret;
+      SCM (*subr)();
+
+      SCM_UNPACK_RTL_24 (op, ptr_idx);
+
+      pointer = FREE_VARIABLE_REF (ptr_idx);
+      subr = SCM_POINTER_VALUE (pointer);
+
+      VM_HANDLE_INTERRUPTS;
+      SYNC_IP ();
+
+      switch (FRAME_LOCALS_COUNT ())
+        {
+        case 0:
+          ret = subr ();
+          break;
+        case 1:
+          ret = subr (fp[0]);
+          break;
+        case 2:
+          ret = subr (fp[0], fp[1]);
+          break;
+        case 3:
+          ret = subr (fp[0], fp[1], fp[2]);
+          break;
+        case 4:
+          ret = subr (fp[0], fp[1], fp[2], fp[3]);
+          break;
+        case 5:
+          ret = subr (fp[0], fp[1], fp[2], fp[3], fp[4]);
+          break;
+        case 6:
+          ret = subr (fp[0], fp[1], fp[2], fp[3], fp[4], fp[5]);
+          break;
+        case 7:
+          ret = subr (fp[0], fp[1], fp[2], fp[3], fp[4], fp[5], fp[6]);
+          break;
+        case 8:
+          ret = subr (fp[0], fp[1], fp[2], fp[3], fp[4], fp[5], fp[6], fp[7]);
+          break;
+        case 9:
+          ret = subr (fp[0], fp[1], fp[2], fp[3], fp[4], fp[5], fp[6], fp[7], fp[8]);
+          break;
+        case 10:
+          ret = subr (fp[0], fp[1], fp[2], fp[3], fp[4], fp[5], fp[6], fp[7], fp[8], fp[9]);
+          break;
+        default:
+          abort ();
+        }
+
+      // NULLSTACK_FOR_NONLOCAL_EXIT ();
+
+      if (SCM_UNLIKELY (SCM_VALUESP (ret)))
+        /* multiple values returned to continuation */
+        RETURN_VALUE_LIST (scm_struct_ref (ret, SCM_INUM0));
+      else
+        RETURN_ONE_VALUE (ret);
+    }
+
+  /* foreign-call cif-idx:12 ptr-idx:12
+   *
+   * Call a foreign function.  Fetch the CIF and foreign pointer from
+   * CIF-IDX and PTR-IDX, both free variables.  Return from the calling
+   * frame.  Arguments are taken from the stack.  This instruction is
+   * part of the trampolines created by the FFI, and is not generated by
+   * the compiler.
+   */
+  VM_DEFINE_OP (8, foreign_call, "foreign-call", OP1 (U8_U12_U12))
+    {
+      scm_t_uint16 cif_idx, ptr_idx;
+      SCM cif, pointer, ret;
+
+      SCM_UNPACK_RTL_12_12 (op, cif_idx, ptr_idx);
+
+      cif = FREE_VARIABLE_REF (cif_idx);
+      pointer = FREE_VARIABLE_REF (ptr_idx);
+
+      SYNC_IP ();
+      VM_HANDLE_INTERRUPTS;
+
+      // FIXME: separate args
+      ret = scm_i_foreign_call (scm_cons (cif, pointer), fp);
+
+      // NULLSTACK_FOR_NONLOCAL_EXIT ();
+
+      if (SCM_UNLIKELY (SCM_VALUESP (ret)))
+        /* multiple values returned to continuation */
+        RETURN_VALUE_LIST (scm_struct_ref (ret, SCM_INUM0));
+      else
+        RETURN_ONE_VALUE (ret);
+    }
+
+  /* continuation-call contregs:24
+   *
+   * Return to a continuation, nonlocally.  The arguments to the
+   * continuation are taken from the stack.  CONTREGS is a free variable
+   * containing the reified continuation.  This instruction is part of
+   * the implementation of undelimited continuations, and is not
+   * generated by the compiler.
+   */
+  VM_DEFINE_OP (9, continuation_call, "continuation-call", OP1 (U8_U24))
+    {
+      SCM contregs;
+      scm_t_uint32 contregs_idx;
+
+      SCM_UNPACK_RTL_24 (op, contregs_idx);
+
+      contregs = FREE_VARIABLE_REF (contregs_idx);
+
+      SYNC_IP ();
+      scm_i_check_continuation (contregs);
+      vm_return_to_continuation (scm_i_contregs_vm (contregs),
+                                 scm_i_contregs_vm_cont (contregs),
+                                 FRAME_LOCALS_COUNT (), fp);
+      scm_i_reinstate_continuation (contregs);
+
+      /* no NEXT */
+      abort ();
+    }
+
+  /* compose-continuation cont:24
+   *
+   * Compose a partial continution with the current continuation.  The
+   * arguments to the continuation are taken from the stack.  CONT is a
+   * free variable containing the reified continuation.  This
+   * instruction is part of the implementation of partial continuations,
+   * and is not generated by the compiler.
+   */
+  VM_DEFINE_OP (10, compose_continuation, "compose-continuation", OP1 (U8_U24))
+    {
+      SCM vmcont;
+      scm_t_uint32 cont_idx;
+
+      SCM_UNPACK_RTL_24 (op, cont_idx);
+      vmcont = LOCAL_REF (cont_idx);
+
+      SYNC_IP ();
+      VM_ASSERT (SCM_VM_CONT_REWINDABLE_P (vmcont),
+                 vm_error_continuation_not_rewindable (vmcont));
+      vm_reinstate_partial_continuation (vm, vmcont, FRAME_LOCALS_COUNT (), fp,
+                                         &current_thread->dynstack,
+                                         &registers);
+      CACHE_REGISTER ();
+      NEXT (0);
+    }
+
+  /* apply _:24
+   *
+   * Tail-apply the procedure in local slot 0 to the rest of the
+   * arguments.  This instruction is part of the implementation of
+   * `apply', and is not generated by the compiler.
+   */
+  VM_DEFINE_OP (11, apply, "apply", OP1 (U8_X24))
+    {
+      int i, list_idx, list_len, nargs;
+      SCM list;
+
+      VM_HANDLE_INTERRUPTS;
+
+      VM_ASSERT (FRAME_LOCALS_COUNT () >= 2, abort ());
+      nargs = FRAME_LOCALS_COUNT ();
+      list_idx = nargs - 1;
+      list = LOCAL_REF (list_idx);
+      list_len = scm_ilength (list);
+
+      VM_ASSERT (list_len >= 0, vm_error_apply_to_non_list (list));
+
+      nargs = nargs - 2 + list_len;
+      ALLOC_FRAME (nargs);
+
+      for (i = 0; i < list_idx; i++)
+        fp[i - 1] = fp[i];
+
+      /* Null out these slots, just in case there are less than 2 elements
+         in the list. */
+      fp[list_idx - 1] = SCM_UNDEFINED;
+      fp[list_idx] = SCM_UNDEFINED;
+
+      for (i = 0; i < list_len; i++, list = SCM_CDR (list))
+        fp[list_idx - 1 + i] = SCM_CAR (list);
+
+      APPLY_HOOK ();
+
+      if (SCM_UNLIKELY (!SCM_RTL_PROGRAM_P (SCM_FRAME_PROGRAM (fp))))
+        goto apply;
+
+      ip = SCM_RTL_PROGRAM_CODE (SCM_FRAME_PROGRAM (fp));
+      NEXT (0);
+    }
+
+  /* call/cc _:24
+   *
+   * Capture the current continuation, and tail-apply the procedure in
+   * local slot 0 to it.  This instruction is part of the implementation
+   * of `call/cc', and is not generated by the compiler.
+   */
+  VM_DEFINE_OP (12, call_cc, "call/cc", OP1 (U8_X24))
+#if 0
+    {
+      SCM vm_cont, cont;
+      scm_t_dynstack *dynstack;
+
+      VM_HANDLE_INTERRUPTS;
+
+      SYNC_IP ();
+      dynstack = scm_dynstack_capture_all (&current_thread->dynstack);
+      vm_cont = scm_i_vm_capture_stack (vp->stack_base,
+                                        SCM_FRAME_DYNAMIC_LINK (fp),
+                                        SCM_FRAME_LOWER_ADDRESS (fp) - 1,
+                                        SCM_FRAME_RETURN_ADDRESS (fp),
+                                        SCM_FRAME_MV_RETURN_ADDRESS (fp),
+                                        dynstack,
+                                        0);
+      cont = scm_i_make_continuation (&registers, vm, vm_cont);
+
+      fp[-1] = fp[0];
+      fp[0] = cont;
+      RESET_FRAME (1);
+
+      APPLY_HOOK ();
+
+      if (SCM_UNLIKELY (!SCM_RTL_PROGRAM_P (SCM_FRAME_PROGRAM (fp))))
+        goto apply;
+
+      ip = SCM_RTL_PROGRAM_CODE (SCM_FRAME_PROGRAM (fp));
+      NEXT (0);
+    }
+#else
+  abort();
+#endif
+
+  /* values _:24
+   *
+   * Return all values on the stack to the current continuation.
+   * This instruction is part of the implementation of
+   * `values', and is not generated by the compiler.
+   */
+  VM_DEFINE_OP (13, values, "values", OP1 (U8_X24))
+    {
+      SCM *base = fp;
+#if VM_USE_HOOKS
+      int nargs = FRAME_LOCALS_COUNT ();
+#endif
+
+      /* We don't do much; it's the caller that's responsible for
+         shuffling values and resetting the stack.  */
+
+      VM_HANDLE_INTERRUPTS;
+      ip = SCM_FRAME_RTL_MV_RETURN_ADDRESS (fp);
+      fp = vp->fp = SCM_FRAME_DYNAMIC_LINK (fp);
+
+      /* Clear stack frame.  */
+      base[-1] = SCM_BOOL_F;
+      base[-2] = SCM_BOOL_F;
+      base[-3] = SCM_BOOL_F;
+      base[-4] = SCM_BOOL_F;
+
+      POP_CONTINUATION_HOOK (base, nargs);
+
+      NEXT (0);
+    }
+
+
+  
+
+  /*
+   * Function prologues
+   */
+
+  /* br-if-nargs-ne expected:24 _:8 offset:24
+   * br-if-nargs-lt expected:24 _:8 offset:24
+   * br-if-nargs-gt expected:24 _:8 offset:24
+   *
+   * If the number of actual arguments is not equal, less than, or greater
+   * than EXPECTED, respectively, add OFFSET, a signed 24-bit number, to
+   * the current instruction pointer.
+   */
+  VM_DEFINE_OP (14, br_if_nargs_ne, "br-if-nargs-ne", OP2 (U8_U24, X8_L24))
+    {
+      BR_NARGS (!=);
+    }
+  VM_DEFINE_OP (15, br_if_nargs_lt, "br-if-nargs-lt", OP2 (U8_U24, X8_L24))
+    {
+      BR_NARGS (<);
+    }
+  VM_DEFINE_OP (16, br_if_nargs_gt, "br-if-nargs-gt", OP2 (U8_U24, X8_L24))
+    {
+      BR_NARGS (>);
+    }
+
+  /* assert-nargs-ee expected:24
+   * assert-nargs-ge expected:24
+   * assert-nargs-le expected:24
+   *
+   * If the number of actual arguments is not ==, >=, or <= EXPECTED,
+   * respectively, signal an error.
+   */
+  VM_DEFINE_OP (17, assert_nargs_ee, "assert-nargs-ee", OP1 (U8_U24))
+    {
+      scm_t_uint32 expected;
+      SCM_UNPACK_RTL_24 (op, expected);
+      VM_ASSERT (FRAME_LOCALS_COUNT () == expected,
+                 vm_error_wrong_num_args (SCM_FRAME_PROGRAM (fp)));
+      NEXT (1);
+    }
+  VM_DEFINE_OP (18, assert_nargs_ge, "assert-nargs-ge", OP1 (U8_U24))
+    {
+      scm_t_uint32 expected;
+      SCM_UNPACK_RTL_24 (op, expected);
+      VM_ASSERT (FRAME_LOCALS_COUNT () >= expected,
+                 vm_error_wrong_num_args (SCM_FRAME_PROGRAM (fp)));
+      NEXT (1);
+    }
+  VM_DEFINE_OP (19, assert_nargs_le, "assert-nargs-le", OP1 (U8_U24))
+    {
+      scm_t_uint32 expected;
+      SCM_UNPACK_RTL_24 (op, expected);
+      VM_ASSERT (FRAME_LOCALS_COUNT () <= expected,
+                 vm_error_wrong_num_args (SCM_FRAME_PROGRAM (fp)));
+      NEXT (1);
+    }
+
+  /* reserve-locals nlocals:24
+   *
+   * Ensure that there is space on the stack for NLOCALS local variables,
+   * setting them all to SCM_UNDEFINED, except those nargs values that
+   * were passed as arguments.
+   */
+  VM_DEFINE_OP (20, reserve_locals, "reserve-locals", OP1 (U8_U24))
+    {
+      scm_t_uint32 nlocals, nargs;
+      SCM_UNPACK_RTL_24 (op, nlocals);
+
+      nargs = FRAME_LOCALS_COUNT ();
+      ALLOC_FRAME (nlocals);
+      while (nlocals-- > nargs)
+        LOCAL_SET (nlocals, SCM_UNDEFINED);
+
+      NEXT (1);
+    }
+
+  /* assert-nargs-ee/locals expected:12 nlocals:12
+   *
+   * Equivalent to a sequence of assert-nargs-ee and reserve-locals.  The
+   * number of locals reserved is EXPECTED + NLOCALS.
+   */
+  VM_DEFINE_OP (21, assert_nargs_ee_locals, "assert-nargs-ee/locals", OP1 (U8_U12_U12))
+    {
+      scm_t_uint16 expected, nlocals;
+      SCM_UNPACK_RTL_12_12 (op, expected, nlocals);
+      VM_ASSERT (FRAME_LOCALS_COUNT () == expected,
+                 vm_error_wrong_num_args (SCM_FRAME_PROGRAM (fp)));
+      ALLOC_FRAME (expected + nlocals);
+      while (nlocals--)
+        LOCAL_SET (expected + nlocals, SCM_UNDEFINED);
+
+      NEXT (1);
+    }
+
+  /* bind-kwargs nreq:24 allow-other-keys:1 has-rest:1 _:6 nreq-and-opt:24
+   * _:8 ntotal:24 kw-offset:32
+   *
+   * Find the last positional argument, and shuffle all the rest above
+   * NTOTAL.  Initialize the intervening locals to SCM_UNDEFINED.  Then
+   * load the constant at KW-OFFSET words from the current IP, and use it
+   * to bind keyword arguments.  If HAS-REST, collect all shuffled
+   * arguments into a list, and store it in NREQ-AND-OPT.  Finally, clear
+   * the arguments that we shuffled up.
+   *
+   * A macro-mega-instruction.
+   */
+  VM_DEFINE_OP (22, bind_kwargs, "bind-kwargs", OP4 (U8_U24, U8_U24, X8_U24, N32))
+    {
+      scm_t_uint32 nreq, nreq_and_opt, ntotal, npositional, nkw, n, nargs;
+      scm_t_int32 kw_offset;
+      scm_t_bits kw_bits;
+      SCM kw;
+      char allow_other_keys, has_rest;
+
+      SCM_UNPACK_RTL_24 (op, nreq);
+      allow_other_keys = ip[1] & 0x1;
+      has_rest = ip[1] & 0x2;
+      SCM_UNPACK_RTL_24 (ip[1], nreq_and_opt);
+      SCM_UNPACK_RTL_24 (ip[2], ntotal);
+      kw_offset = ip[3];
+      kw_bits = (scm_t_bits) (ip + kw_offset);
+      VM_ASSERT (!(kw_bits & 0x7), abort());
+      kw = SCM_PACK (kw_bits);
+
+      nargs = FRAME_LOCALS_COUNT ();
+
+      /* look in optionals for first keyword or last positional */
+      /* starting after the last required positional arg */
+      npositional = nreq;
+      while (/* while we have args */
+             npositional < nargs
+             /* and we still have positionals to fill */
+             && npositional < nreq_and_opt
+             /* and we haven't reached a keyword yet */
+             && !scm_is_keyword (LOCAL_REF (npositional)))
+        /* bind this optional arg (by leaving it in place) */
+        npositional++;
+      nkw = nargs - npositional;
+      /* shuffle non-positional arguments above ntotal */
+      ALLOC_FRAME (ntotal + nkw);
+      n = nkw;
+      while (n--)
+        LOCAL_SET (ntotal + n, LOCAL_REF (npositional + n));
+      /* and fill optionals & keyword args with SCM_UNDEFINED */
+      n = npositional;
+      while (n < ntotal)
+        LOCAL_SET (n++, SCM_UNDEFINED);
+
+      VM_ASSERT (has_rest || (nkw % 2) == 0,
+                 vm_error_kwargs_length_not_even (SCM_FRAME_PROGRAM (fp)));
+
+      /* Now bind keywords, in the order given.  */
+      for (n = 0; n < nkw; n++)
+        if (scm_is_keyword (LOCAL_REF (ntotal + n)))
+          {
+            SCM walk;
+            for (walk = kw; scm_is_pair (walk); walk = SCM_CDR (walk))
+              if (scm_is_eq (SCM_CAAR (walk), LOCAL_REF (ntotal + n)))
+                {
+                  SCM si = SCM_CDAR (walk);
+                  LOCAL_SET (SCM_I_INUMP (si) ? SCM_I_INUM (si) : scm_to_uint32 (si),
+                             LOCAL_REF (ntotal + n + 1));
+                  break;
+                }
+            VM_ASSERT (scm_is_pair (walk) || allow_other_keys,
+                       vm_error_kwargs_unrecognized_keyword (SCM_FRAME_PROGRAM (fp)));
+            n++;
+          }
+        else
+          VM_ASSERT (has_rest, vm_error_kwargs_invalid_keyword (SCM_FRAME_PROGRAM (fp)));
+
+      if (has_rest)
+        {
+          SCM rest = SCM_EOL;
+          n = nkw;
+          while (n--)
+            rest = scm_cons (LOCAL_REF (ntotal + n), rest);
+          LOCAL_SET (nreq_and_opt, rest);
+        }
+
+      RESET_FRAME (ntotal);
+
+      NEXT (4);
+    }
+
+  /* bind-rest dst:24
+   *
+   * Collect any arguments at or above DST into a list, and store that
+   * list at DST.
+   */
+  VM_DEFINE_OP (23, bind_rest, "bind-rest", OP1 (U8_U24) | OP_DST)
+    {
+      scm_t_uint32 dst, nargs;
+      SCM rest = SCM_EOL;
+
+      SCM_UNPACK_RTL_24 (op, dst);
+      nargs = FRAME_LOCALS_COUNT ();
+
+      while (nargs-- > dst)
+        {
+          rest = scm_cons (LOCAL_REF (nargs), rest);
+          LOCAL_SET (nargs, SCM_UNDEFINED);
+        }
+
+      LOCAL_SET (dst, rest);
+
+      RESET_FRAME (dst + 1);
+
+      NEXT (1);
+    }
+
+  /* drop-values nlocals:24
+   *
+   * Reset the stack pointer to only have space for NLOCALS values.
+   * Used after extracting values from an MV return.
+   */
+  VM_DEFINE_OP (24, drop_values, "drop-values", OP1 (U8_U24))
+    {
+      scm_t_bits nlocals;
+
+      SCM_UNPACK_RTL_24 (op, nlocals);
+
+      RESET_FRAME (nlocals);
+
+      NEXT (1);
+    }
+
+
+  
+
+  /*
+   * Branching instructions
+   */
+
+  /* br offset:24
+   *
+   * Add OFFSET, a signed 24-bit number, to the current instruction
+   * pointer.
+   */
+  VM_DEFINE_OP (25, br, "br", OP1 (U8_L24))
+    {
+      scm_t_int32 offset = op;
+      offset >>= 8; /* Sign-extending shift. */
+      NEXT (offset);
+    }
+
+  /* br-if-true test:24 invert:1 _:7 offset:24
+   *
+   * If the value in TEST is true for the purposes of Scheme, add
+   * OFFSET, a signed 24-bit number, to the current instruction pointer.
+   */
+  VM_DEFINE_OP (26, br_if_true, "br-if-true", OP2 (U8_U24, B1_X7_L24))
+    {
+      BR_UNARY (x, scm_is_true (x));
+    }
+
+  /* br-if-null test:24 invert:1 _:7 offset:24
+   *
+   * If the value in TEST is the end-of-list or Lisp nil, add OFFSET, a
+   * signed 24-bit number, to the current instruction pointer.
+   */
+  VM_DEFINE_OP (27, br_if_null, "br-if-null", OP2 (U8_U24, B1_X7_L24))
+    {
+      BR_UNARY (x, scm_is_null (x));
+    }
+
+  /* br-if-nil test:24 invert:1 _:7 offset:24
+   *
+   * If the value in TEST is false to Lisp, add OFFSET, a signed 24-bit
+   * number, to the current instruction pointer.
+   */
+  VM_DEFINE_OP (28, br_if_nil, "br-if-nil", OP2 (U8_U24, B1_X7_L24))
+    {
+      BR_UNARY (x, scm_is_lisp_false (x));
+    }
+
+  /* br-if-pair test:24 invert:1 _:7 offset:24
+   *
+   * If the value in TEST is a pair, add OFFSET, a signed 24-bit number,
+   * to the current instruction pointer.
+   */
+  VM_DEFINE_OP (29, br_if_pair, "br-if-pair", OP2 (U8_U24, B1_X7_L24))
+    {
+      BR_UNARY (x, scm_is_pair (x));
+    }
+
+  /* br-if-struct test:24 invert:1 _:7 offset:24
+   *
+   * If the value in TEST is a struct, add OFFSET, a signed 24-bit
+   * number, to the current instruction pointer.
+   */
+  VM_DEFINE_OP (30, br_if_struct, "br-if-struct", OP2 (U8_U24, B1_X7_L24))
+    {
+      BR_UNARY (x, SCM_STRUCTP (x));
+    }
+
+  /* br-if-char test:24 invert:1 _:7 offset:24
+   *
+   * If the value in TEST is a char, add OFFSET, a signed 24-bit number,
+   * to the current instruction pointer.
+   */
+  VM_DEFINE_OP (31, br_if_char, "br-if-char", OP2 (U8_U24, B1_X7_L24))
+    {
+      BR_UNARY (x, SCM_CHARP (x));
+    }
+
+  /* br-if-tc7 test:24 invert:1 tc7:7 offset:24
+   *
+   * If the value in TEST has the TC7 given in the second word, add
+   * OFFSET, a signed 24-bit number, to the current instruction pointer.
+   */
+  VM_DEFINE_OP (32, br_if_tc7, "br-if-tc7", OP2 (U8_U24, B1_U7_L24))
+    {
+      BR_UNARY (x, SCM_HAS_TYP7 (x, (ip[1] >> 1) & 0x7f));
+    }
+
+  /* br-if-eq a:12 b:12 invert:1 _:7 offset:24
+   *
+   * If the value in A is eq? to the value in B, add OFFSET, a signed
+   * 24-bit number, to the current instruction pointer.
+   */
+  VM_DEFINE_OP (33, br_if_eq, "br-if-eq", OP2 (U8_U12_U12, B1_X7_L24))
+    {
+      BR_BINARY (x, y, scm_is_eq (x, y));
+    }
+
+  /* br-if-eqv a:12 b:12 invert:1 _:7 offset:24
+   *
+   * If the value in A is eqv? to the value in B, add OFFSET, a signed
+   * 24-bit number, to the current instruction pointer.
+   */
+  VM_DEFINE_OP (34, br_if_eqv, "br-if-eqv", OP2 (U8_U12_U12, B1_X7_L24))
+    {
+      BR_BINARY (x, y,
+                 scm_is_eq (x, y)
+                 || (SCM_NIMP (x) && SCM_NIMP (y)
+                     && scm_is_true (scm_eqv_p (x, y))));
+    }
+
+  /* br-if-equal a:12 b:12 invert:1 _:7 offset:24
+   *
+   * If the value in A is equal? to the value in B, add OFFSET, a signed
+   * 24-bit number, to the current instruction pointer.
+   */
+  // FIXME: should sync_ip before calling out?
+  VM_DEFINE_OP (35, br_if_equal, "br-if-equal", OP2 (U8_U12_U12, B1_X7_L24))
+    {
+      BR_BINARY (x, y,
+                 scm_is_eq (x, y)
+                 || (SCM_NIMP (x) && SCM_NIMP (y)
+                     && scm_is_true (scm_equal_p (x, y))));
+    }
+
+  /* br-if-= a:12 b:12 _:8 offset:24
+   *
+   * If the value in A is = to the value in B, add OFFSET, a signed
+   * 24-bit number, to the current instruction pointer.
+   */
+  VM_DEFINE_OP (36, br_if_ee, "br-if-=", OP2 (U8_U12_U12, X8_L24))
+    {
+      BR_ARITHMETIC (==, scm_num_eq_p);
+    }
+
+  /* br-if-< a:12 b:12 _:8 offset:24
+   *
+   * If the value in A is < to the value in B, add OFFSET, a signed
+   * 24-bit number, to the current instruction pointer.
+   */
+  VM_DEFINE_OP (37, br_if_lt, "br-if-<", OP2 (U8_U12_U12, X8_L24))
+    {
+      BR_ARITHMETIC (<, scm_less_p);
+    }
+
+  /* br-if-<= a:12 b:12 _:8 offset:24
+   *
+   * If the value in A is <= to the value in B, add OFFSET, a signed
+   * 24-bit number, to the current instruction pointer.
+   */
+  VM_DEFINE_OP (38, br_if_le, "br-if-<=", OP2 (U8_U12_U12, X8_L24))
+    {
+      BR_ARITHMETIC (<=, scm_leq_p);
+    }
+
+  /* br-if-> a:12 b:12 _:8 offset:24
+   *
+   * If the value in A is > to the value in B, add OFFSET, a signed
+   * 24-bit number, to the current instruction pointer.
+   */
+  VM_DEFINE_OP (39, br_if_gt, "br-if->", OP2 (U8_U12_U12, X8_L24))
+    {
+      BR_ARITHMETIC (>, scm_gr_p);
+    }
+
+  /* br-if->= a:12 b:12 _:8 offset:24
+   *
+   * If the value in A is >= to the value in B, add OFFSET, a signed
+   * 24-bit number, to the current instruction pointer.
+   */
+  VM_DEFINE_OP (40, br_if_ge, "br-if->=", OP2 (U8_U12_U12, X8_L24))
+    {
+      BR_ARITHMETIC (>=, scm_geq_p);
+    }
+
+
+  
+
+  /*
+   * Lexical binding instructions
+   */
+
+  /* mov dst:12 src:12
+   *
+   * Copy a value from one local slot to another.
+   */
+  VM_DEFINE_OP (41, mov, "mov", OP1 (U8_U12_U12) | OP_DST)
+    {
+      scm_t_uint16 dst;
+      scm_t_uint16 src;
+
+      SCM_UNPACK_RTL_12_12 (op, dst, src);
+      LOCAL_SET (dst, LOCAL_REF (src));
+
+      NEXT (1);
+    }
+
+  /* long-mov dst:24 _:8 src:24
+   *
+   * Copy a value from one local slot to another.
+   */
+  VM_DEFINE_OP (42, long_mov, "long-mov", OP2 (U8_U24, X8_U24) | OP_DST)
+    {
+      scm_t_uint32 dst;
+      scm_t_uint32 src;
+
+      SCM_UNPACK_RTL_24 (op, dst);
+      SCM_UNPACK_RTL_24 (ip[1], src);
+      LOCAL_SET (dst, LOCAL_REF (src));
+
+      NEXT (2);
+    }
+
+  /* box dst:12 src:12
+   *
+   * Create a new variable holding SRC, and place it in DST.
+   */
+  VM_DEFINE_OP (43, box, "box", OP1 (U8_U12_U12) | OP_DST)
+    {
+      scm_t_uint16 dst, src;
+      SCM_UNPACK_RTL_12_12 (op, dst, src);
+      LOCAL_SET (dst, scm_cell (scm_tc7_variable, SCM_UNPACK (LOCAL_REF (src))));
+      NEXT (1);
+    }
+
+  /* empty-box dst:24
+   *
+   * Create a new unbound variable, and place it in DST.  Used in the
+   * general implementation of `letrec', in those cases that fix-letrec
+   * fails to fix.
+   */
+  VM_DEFINE_OP (44, empty_box, "empty-box", OP1 (U8_U24) | OP_DST)
+    {
+      scm_t_uint32 dst;
+      SCM_UNPACK_RTL_24 (op, dst);
+      LOCAL_SET (dst, scm_cell (scm_tc7_variable, SCM_UNPACK (SCM_UNDEFINED)));
+      NEXT (1);
+    }
+
+  /* box-ref dst:12 src:12
+   *
+   * Unpack the variable at SRC into DST, asserting that the variable is
+   * actually bound.
+   */
+  VM_DEFINE_OP (45, box_ref, "box-ref", OP1 (U8_U12_U12) | OP_DST)
+    {
+      scm_t_uint16 dst, src;
+      SCM var;
+      SCM_UNPACK_RTL_12_12 (op, dst, src);
+      var = LOCAL_REF (src);
+      VM_ASSERT (SCM_VARIABLEP (var), abort ());
+      if (SCM_UNLIKELY (!VARIABLE_BOUNDP (var)))
+        {
+          SCM var_name;
+          /* Attempt to provide the variable name in the error message.  */
+          SYNC_IP ();
+          var_name = scm_module_reverse_lookup (scm_current_module (), var);
+          vm_error_unbound (SCM_FRAME_PROGRAM (fp), scm_is_true (var_name) ? var_name : var);
+        }
+      LOCAL_SET (dst, VARIABLE_REF (var));
+      NEXT (1);
+    }
+
+  /* box-set! dst:12 src:12
+   *
+   * Set the contents of the variable at DST to SET.
+   */
+  VM_DEFINE_OP (46, box_set, "box-set!", OP1 (U8_U12_U12) | OP_DST)
+    {
+      scm_t_uint16 dst, src;
+      SCM var;
+      SCM_UNPACK_RTL_12_12 (op, dst, src);
+      var = LOCAL_REF (dst);
+      VM_ASSERT (SCM_VARIABLEP (var), abort ());
+      VARIABLE_SET (var, LOCAL_REF (src));
+      NEXT (1);
+    }
+
+  /* free-ref dst:12 src:12
+   *
+   * Load free variable SRC into local slot DST.
+   */
+  VM_DEFINE_OP (47, free_ref, "free-ref", OP1 (U8_U12_U12) | OP_DST)
+    {
+      scm_t_uint16 dst, src;
+      SCM_UNPACK_RTL_12_12 (op, dst, src);
+      CHECK_FREE_VARIABLE (src);
+      LOCAL_SET (dst, FREE_VARIABLE_REF (src));
+      NEXT (1);
+    }
+
+  /* make-closure dst:24 offset:32 _:8 nfree:24 free0:24 0:8 ...
+   *
+   * Make a new closure, and write it to DST.  The code for the closure
+   * will be found at OFFSET words from the current IP.  OFFSET is a
+   * signed 32-bit integer.  The registers for the NFREE free variables
+   * follow.
+   */
+  VM_DEFINE_OP (48, make_closure, "make-closure", OP3 (U8_U24, L32, X8_R24) | OP_DST)
+    {
+      scm_t_uint32 dst, nfree, n;
+      scm_t_int32 offset;
+      SCM closure;
+
+      SCM_UNPACK_RTL_24 (op, dst);
+      offset = ip[1];
+      SCM_UNPACK_RTL_24 (ip[2], nfree);
+
+      // FIXME: Assert range of nfree?
+      closure = scm_words (scm_tc7_rtl_program | (nfree << 16), nfree + 2);
+      SCM_SET_CELL_WORD_1 (closure, ip + offset);
+      for (n = 0; n < nfree; n++)
+        SCM_RTL_PROGRAM_FREE_VARIABLE_SET (closure, n, LOCAL_REF (ip[n + 3]));
+      LOCAL_SET (dst, closure);
+      NEXT (nfree + 3);
+    }
+
+  /* fix-closure dst:24 _:8 nfree:24 free0:24 0:8 ...
+   *
+   * "Fix" a closure.  This is used for lambda expressions bound in a
+   * <fix>, but which are not always called in tail position.  In that
+   * case we allocate the closures first, then destructively update their
+   * free variables to point to each other.  NFREE and the locals FREE0...
+   * are as in make-closure.
+   */
+  VM_DEFINE_OP (49, fix_closure, "fix-closure", OP2 (U8_U24, X8_R24))
+    {
+      scm_t_uint32 dst, nfree, n;
+      SCM closure;
+
+      SCM_UNPACK_RTL_24 (op, dst);
+      SCM_UNPACK_RTL_24 (ip[1], nfree);
+      closure = LOCAL_REF (dst);
+      for (n = 0; n < nfree; n++)
+        SCM_RTL_PROGRAM_FREE_VARIABLE_SET (closure, n, LOCAL_REF (ip[n + 2]));
+      NEXT (nfree + 2);
+    }
+
+
+  
+
+  /*
+   * Immediates and statically allocated non-immediates
+   */
+
+  /* make-short-immediate dst:8 low-bits:16
+   *
+   * Make an immediate whose low bits are LOW-BITS, and whose top bits are
+   * 0.
+   */
+  VM_DEFINE_OP (50, make_short_immediate, "make-short-immediate", OP1 (U8_U8_I16) | OP_DST)
+    {
+      scm_t_uint8 dst;
+      scm_t_bits val;
+
+      SCM_UNPACK_RTL_8_16 (op, dst, val);
+      LOCAL_SET (dst, SCM_PACK (val));
+      NEXT (1);
+    }
+
+  /* make-long-immediate dst:24 low-bits:32
+   *
+   * Make an immediate whose low bits are LOW-BITS, and whose top bits are
+   * 0.
+   */
+  VM_DEFINE_OP (51, make_long_immediate, "make-long-immediate", OP2 (U8_U24, I32))
+    {
+      scm_t_uint8 dst;
+      scm_t_bits val;
+
+      SCM_UNPACK_RTL_24 (op, dst);
+      val = ip[1];
+      LOCAL_SET (dst, SCM_PACK (val));
+      NEXT (2);
+    }
+
+  /* make-long-long-immediate dst:24 high-bits:32 low-bits:32
+   *
+   * Make an immediate with HIGH-BITS and LOW-BITS.
+   */
+  VM_DEFINE_OP (52, make_long_long_immediate, "make-long-long-immediate", OP3 (U8_U24, A32, B32) | OP_DST)
+    {
+      scm_t_uint8 dst;
+      scm_t_bits val;
+
+      SCM_UNPACK_RTL_24 (op, dst);
+#if SIZEOF_SCM_T_BITS > 4
+      val = ip[1];
+      val <<= 32;
+      val |= ip[2];
+#else
+      ASSERT (ip[1] == 0);
+      val = ip[2];
+#endif
+      LOCAL_SET (dst, SCM_PACK (val));
+      NEXT (3);
+    }
+
+  /* make-non-immediate dst:24 offset:32
+   *
+   * Load a pointer to statically allocated memory into DST.  The
+   * object's memory is will be found OFFSET 32-bit words away from the
+   * current instruction pointer.  OFFSET is a signed value.  The
+   * intention here is that the compiler would produce an object file
+   * containing the words of a non-immediate object, and this
+   * instruction creates a pointer to that memory, effectively
+   * resurrecting that object.
+   *
+   * Whether the object is mutable or immutable depends on where it was
+   * allocated by the compiler, and loaded by the loader.
+   */
+  VM_DEFINE_OP (53, make_non_immediate, "make-non-immediate", OP2 (U8_U24, N32) | OP_DST)
+    {
+      scm_t_uint32 dst;
+      scm_t_int32 offset;
+      scm_t_uint32* loc;
+      scm_t_bits unpacked;
+
+      SCM_UNPACK_RTL_24 (op, dst);
+      offset = ip[1];
+      loc = ip + offset;
+      unpacked = (scm_t_bits) loc;
+
+      VM_ASSERT (!(unpacked & 0x7), abort());
+
+      LOCAL_SET (dst, SCM_PACK (unpacked));
+
+      NEXT (2);
+    }
+
+  /* static-ref dst:24 offset:32
+   *
+   * Load a SCM value into DST.  The SCM value will be fetched from
+   * memory, OFFSET 32-bit words away from the current instruction
+   * pointer.  OFFSET is a signed value.
+   *
+   * The intention is for this instruction to be used to load constants
+   * that the compiler is unable to statically allocate, like symbols.
+   * These values would be initialized when the object file loads.
+   */
+  VM_DEFINE_OP (54, static_ref, "static-ref", OP2 (U8_U24, S32))
+    {
+      scm_t_uint32 dst;
+      scm_t_int32 offset;
+      scm_t_uint32* loc;
+      scm_t_uintptr loc_bits;
+
+      SCM_UNPACK_RTL_24 (op, dst);
+      offset = ip[1];
+      loc = ip + offset;
+      loc_bits = (scm_t_uintptr) loc;
+      VM_ASSERT (ALIGNED_P (loc, SCM), abort());
+
+      LOCAL_SET (dst, *((SCM *) loc_bits));
+
+      NEXT (2);
+    }
+
+  /* static-set! src:24 offset:32
+   *
+   * Store a SCM value into memory, OFFSET 32-bit words away from the
+   * current instruction pointer.  OFFSET is a signed value.
+   */
+  VM_DEFINE_OP (55, static_set, "static-set!", OP2 (U8_U24, LO32))
+    {
+      scm_t_uint32 src;
+      scm_t_int32 offset;
+      scm_t_uint32* loc;
+
+      SCM_UNPACK_RTL_24 (op, src);
+      offset = ip[1];
+      loc = ip + offset;
+      VM_ASSERT (ALIGNED_P (loc, SCM), abort());
+
+      *((SCM *) loc) = LOCAL_REF (src);
+
+      NEXT (2);
+    }
+
+  /* link-procedure! src:24 offset:32
+   *
+   * Set the code pointer of the procedure in SRC to point OFFSET 32-bit
+   * words away from the current instruction pointer.  OFFSET is a
+   * signed value.
+   */
+  VM_DEFINE_OP (56, link_procedure, "link-procedure!", OP2 (U8_U24, L32))
+    {
+      scm_t_uint32 src;
+      scm_t_int32 offset;
+      scm_t_uint32* loc;
+
+      SCM_UNPACK_RTL_24 (op, src);
+      offset = ip[1];
+      loc = ip + offset;
+
+      SCM_SET_CELL_WORD_1 (LOCAL_REF (src), (scm_t_bits) loc);
+
+      NEXT (2);
+    }
+
+  
+
+  /*
+   * Mutable top-level bindings
+   */
+
+  /* There are three slightly different ways to resolve toplevel
+     variables.
+
+     1. A toplevel reference outside of a function.  These need to be
+        looked up when the expression is evaluated -- no later, and no
+        before.  They are looked up relative to the module that is
+        current when the expression is evaluated.  For example:
+
+          (if (foo) a b)
+
+        The "resolve" instruction resolves the variable (box), and then
+        access is via box-ref or box-set!.
+
+     2. A toplevel reference inside a function.  These are looked up
+        relative to the module that was current when the function was
+        defined.  Unlike code at the toplevel, which is usually run only
+        once, these bindings benefit from memoized lookup, in which the
+        variable resulting from the lookup is cached in the function.
+
+          (lambda () (if (foo) a b))
+
+        Although one can use resolve and box-ref, the toplevel-ref and
+        toplevel-set! instructions are better for references.
+
+     3. A reference to an identifier with respect to a particular
+        module.  This can happen for primitive references, and
+        references residualized by macro expansions.  These can be
+        cached or not, depending on whether they are in a lambda or not.
+
+          (@ (foo bar) a)
+          (@@ (foo bar) a)
+
+        For these, one can use resolve-module, resolve, and the box
+        interface, though there is also module-ref as a shortcut.
+     */
+
+  /* current-module dst:24
+   *
+   * Store the current module in DST.
+   */
+  VM_DEFINE_OP (57, current_module, "current-module", OP1 (U8_U24) | OP_DST)
+    {
+      scm_t_uint32 dst;
+
+      SCM_UNPACK_RTL_24 (op, dst);
+
+      SYNC_IP ();
+      LOCAL_SET (dst, scm_current_module ());
+
+      NEXT (1);
+    }
+
+  /* resolve dst:8 mod:8 sym:8
+   *
+   * Resolve SYM in MOD, and place the resulting variable in DST.
+   */
+  VM_DEFINE_OP (58, resolve, "resolve", OP1 (U8_U8_U8_U8) | OP_DST)
+    {
+      scm_t_uint8 dst, mod, sym;
+
+      SCM_UNPACK_RTL_8_8_8 (op, dst, mod, sym);
+
+      SYNC_IP ();
+      LOCAL_SET (dst, scm_module_lookup (LOCAL_REF (mod), LOCAL_REF (sym)));
+
+      NEXT (1);
+    }
+
+  /* resolve-module dst:8 name:8 public:8
+   *
+   * Resolve a module with name NAME, placing it in DST.  If PUBLIC is
+   * nonzero, resolve the public interface, otherwise use the private
+   * interface.
+   */
+  VM_DEFINE_OP (59, resolve_module, "resolve-module", OP1 (U8_U8_U8_U8) | OP_DST)
+    {
+      scm_t_uint8 dst, name, public;
+      SCM mod;
+
+      SCM_UNPACK_RTL_8_8_8 (op, dst, name, public);
+
+      SYNC_IP ();
+      mod = scm_resolve_module (LOCAL_REF (name));
+      if (public)
+        mod = scm_module_public_interface (mod);
+      LOCAL_SET (dst, mod);
+
+      NEXT (1);
+    }
+
+  /* define sym:12 val:12
+   *
+   * Look up a binding for SYM in the current module, creating it if
+   * necessary.  Set its value to VAL.
+   */
+  VM_DEFINE_OP (60, define, "define", OP1 (U8_U12_U12))
+    {
+      scm_t_uint16 sym, val;
+      SCM_UNPACK_RTL_12_12 (op, sym, val);
+      SYNC_IP ();
+      scm_define (LOCAL_REF (sym), LOCAL_REF (val));
+      NEXT (1);
+    }
+
+  /* toplevel-ref dst:24 var-offset:32 mod-offset:32 sym-offset:32
+   *
+   * Load a SCM value.  The SCM value will be fetched from memory,
+   * VAR-OFFSET 32-bit words away from the current instruction pointer.
+   * VAR-OFFSET is a signed value.  Up to here, toplevel-ref is like
+   * static-ref.
+   *
+   * Then, if the loaded value is a variable, the value of the variable
+   * is placed in DST, and control flow continues.
+   *
+   * Otherwise, we have to resolve the variable.  In that case we load
+   * the module from MOD-OFFSET, just as we loaded the variable.
+   * Usually the module gets set when the closure is created.  The name
+   * is an offset to a symbol.
+   *
+   * We use the module and the string to resolve the variable, raising
+   * an error if it is unbound, unbox it into DST, and cache the
+   * resolved variable so that we will hit the cache next time.
+   */
+  VM_DEFINE_OP (61, toplevel_ref, "toplevel-ref", OP4 (U8_U24, S32, S32, N32) | OP_DST)
+    {
+      scm_t_uint32 dst;
+      scm_t_int32 var_offset;
+      scm_t_uint32* var_loc_u32;
+      SCM *var_loc;
+      SCM var;
+
+      SCM_UNPACK_RTL_24 (op, dst);
+      var_offset = ip[1];
+      var_loc_u32 = ip + var_offset;
+      VM_ASSERT (ALIGNED_P (var_loc_u32, SCM), abort());
+      var_loc = (SCM *) var_loc_u32;
+      var = *var_loc;
+
+      if (SCM_UNLIKELY (!SCM_VARIABLEP (var)))
+        {
+          SCM mod, sym;
+          scm_t_int32 mod_offset = ip[2]; /* signed */
+          scm_t_int32 sym_offset = ip[3]; /* signed */
+          scm_t_uint32 *mod_loc = ip + mod_offset;
+          scm_t_uint32 *sym_loc = ip + sym_offset;
+          
+          SYNC_IP ();
+
+          VM_ASSERT (ALIGNED_P (mod_loc, SCM), abort());
+          VM_ASSERT (ALIGNED_P (sym_loc, SCM), abort());
+
+          mod = *((SCM *) mod_loc);
+          sym = *((SCM *) sym_loc);
+
+          var = scm_module_lookup (mod, sym);
+          VM_ASSERT (VARIABLE_BOUNDP (var), vm_error_unbound (fp[-1], sym));
+
+          *var_loc = var;
+        }
+
+      LOCAL_SET (dst, VARIABLE_REF (var));
+      NEXT (4);
+    }
+
+  /* toplevel-set! src:24 var-offset:32 mod-offset:32 sym-offset:32
+   *
+   * Set a top-level variable from a variable cache cell.  The variable
+   * is resolved as in toplevel-ref.
+   */
+  VM_DEFINE_OP (62, toplevel_set, "toplevel-set!", OP4 (U8_U24, S32, S32, N32))
+    {
+      scm_t_uint32 src;
+      scm_t_int32 var_offset;
+      scm_t_uint32* var_loc_u32;
+      SCM *var_loc;
+      SCM var;
+
+      SCM_UNPACK_RTL_24 (op, src);
+      var_offset = ip[1];
+      var_loc_u32 = ip + var_offset;
+      VM_ASSERT (ALIGNED_P (var_loc_u32, SCM), abort());
+      var_loc = (SCM *) var_loc_u32;
+      var = *var_loc;
+
+      if (SCM_UNLIKELY (!SCM_VARIABLEP (var)))
+        {
+          SCM mod, sym;
+          scm_t_int32 mod_offset = ip[2]; /* signed */
+          scm_t_int32 sym_offset = ip[3]; /* signed */
+          scm_t_uint32 *mod_loc = ip + mod_offset;
+          scm_t_uint32 *sym_loc = ip + sym_offset;
+          
+          SYNC_IP ();
+
+          VM_ASSERT (ALIGNED_P (mod_loc, SCM), abort());
+          VM_ASSERT (ALIGNED_P (sym_loc, SCM), abort());
+
+          mod = *((SCM *) mod_loc);
+          sym = *((SCM *) sym_loc);
+
+          var = scm_module_lookup (mod, sym);
+
+          *var_loc = var;
+        }
+
+      VARIABLE_SET (var, LOCAL_REF (src));
+      NEXT (4);
+    }
+
+  /* module-ref dst:24 var-offset:32 mod-offset:32 sym-offset:32
+   *
+   * Like toplevel-ref, except MOD-OFFSET points at the name of a module
+   * instead of the module itself.
+   */
+  VM_DEFINE_OP (63, module_ref, "module-ref", OP4 (U8_U24, S32, N32, N32) | OP_DST)
+    {
+      scm_t_uint32 dst;
+      scm_t_int32 var_offset;
+      scm_t_uint32* var_loc_u32;
+      SCM *var_loc;
+      SCM var;
+
+      SCM_UNPACK_RTL_24 (op, dst);
+      var_offset = ip[1];
+      var_loc_u32 = ip + var_offset;
+      VM_ASSERT (ALIGNED_P (var_loc_u32, SCM), abort());
+      var_loc = (SCM *) var_loc_u32;
+      var = *var_loc;
+
+      if (SCM_UNLIKELY (!SCM_VARIABLEP (var)))
+        {
+          SCM modname, sym;
+          scm_t_int32 modname_offset = ip[2]; /* signed */
+          scm_t_int32 sym_offset = ip[3]; /* signed */
+          scm_t_uint32 *modname_words = ip + modname_offset;
+          scm_t_uint32 *sym_loc = ip + sym_offset;
+
+          SYNC_IP ();
+
+          VM_ASSERT (!(((scm_t_uintptr) modname_words) & 0x7), abort());
+          VM_ASSERT (ALIGNED_P (sym_loc, SCM), abort());
+
+          modname = SCM_PACK ((scm_t_bits) modname_words);
+          sym = *((SCM *) sym_loc);
+
+          if (scm_is_true (SCM_CAR (modname)))
+            var = scm_public_lookup (SCM_CDR (modname), sym);
+          else
+            var = scm_private_lookup (SCM_CDR (modname), sym);
+
+          VM_ASSERT (VARIABLE_BOUNDP (var), vm_error_unbound (fp[-1], sym));
+
+          *var_loc = var;
+        }
+
+      LOCAL_SET (dst, VARIABLE_REF (var));
+      NEXT (4);
+    }
+
+  /* module-set! src:24 var-offset:32 mod-offset:32 sym-offset:32
+   *
+   * Like toplevel-set!, except MOD-OFFSET points at the name of a module
+   * instead of the module itself.
+   */
+  VM_DEFINE_OP (64, module_set, "module-set!", OP4 (U8_U24, S32, N32, N32))
+    {
+      scm_t_uint32 src;
+      scm_t_int32 var_offset;
+      scm_t_uint32* var_loc_u32;
+      SCM *var_loc;
+      SCM var;
+
+      SCM_UNPACK_RTL_24 (op, src);
+      var_offset = ip[1];
+      var_loc_u32 = ip + var_offset;
+      VM_ASSERT (ALIGNED_P (var_loc_u32, SCM), abort());
+      var_loc = (SCM *) var_loc_u32;
+      var = *var_loc;
+
+      if (SCM_UNLIKELY (!SCM_VARIABLEP (var)))
+        {
+          SCM modname, sym;
+          scm_t_int32 modname_offset = ip[2]; /* signed */
+          scm_t_int32 sym_offset = ip[3]; /* signed */
+          scm_t_uint32 *modname_words = ip + modname_offset;
+          scm_t_uint32 *sym_loc = ip + sym_offset;
+
+          SYNC_IP ();
+
+          VM_ASSERT (!(((scm_t_uintptr) modname_words) & 0x7), abort());
+          VM_ASSERT (ALIGNED_P (sym_loc, SCM), abort());
+
+          modname = SCM_PACK ((scm_t_bits) modname_words);
+          sym = *((SCM *) sym_loc);
+
+          if (scm_is_true (SCM_CAR (modname)))
+            var = scm_public_lookup (SCM_CDR (modname), sym);
+          else
+            var = scm_private_lookup (SCM_CDR (modname), sym);
+
+          *var_loc = var;
+        }
+
+      VARIABLE_SET (var, LOCAL_REF (src));
+      NEXT (4);
+    }
+
+  
+
+  /*
+   * The dynamic environment
+   */
+
+  /* prompt tag:24 flags:8 handler-offset:24
+   *
+   * Push a new prompt on the dynamic stack, with a tag from TAG and a
+   * handler at HANDLER-OFFSET words from the current IP.  The handler
+   * will expect a multiple-value return.
+   */
+  VM_DEFINE_OP (65, prompt, "prompt", OP2 (U8_U24, U8_L24))
+#if 0
+    {
+      scm_t_uint32 tag;
+      scm_t_int32 offset;
+      scm_t_uint8 escape_only_p;
+      scm_t_dynstack_prompt_flags flags;
+
+      SCM_UNPACK_RTL_24 (op, tag);
+      escape_only_p = ip[1] & 0xff;
+      offset = ip[1];
+      offset >>= 8; /* Sign extension */
+  
+      /* Push the prompt onto the dynamic stack. */
+      flags = escape_only_p ? SCM_F_DYNSTACK_PROMPT_ESCAPE_ONLY : 0;
+      scm_dynstack_push_prompt (&current_thread->dynstack, flags,
+                                LOCAL_REF (tag),
+                                fp, vp->sp, ip + offset, &registers);
+      NEXT (2);
+    }
+#else
+  abort();
+#endif
+
+  /* wind winder:12 unwinder:12
+   *
+   * Push wind and unwind procedures onto the dynamic stack. Note that
+   * neither are actually called; the compiler should emit calls to wind
+   * and unwind for the normal dynamic-wind control flow.  Also note that
+   * the compiler should have inserted checks that they wind and unwind
+   * procs are thunks, if it could not prove that to be the case.
+   */
+  VM_DEFINE_OP (66, wind, "wind", OP1 (U8_U12_U12))
+    {
+      scm_t_uint16 winder, unwinder;
+      SCM_UNPACK_RTL_12_12 (op, winder, unwinder);
+      scm_dynstack_push_dynwind (&current_thread->dynstack,
+                                 LOCAL_REF (winder), LOCAL_REF (unwinder));
+      NEXT (1);
+    }
+
+  /* abort tag:24 _:8 nvalues:24 val0:24 0:8 val1:24 0:8 ...
+   *
+   * Return a number of values to a prompt handler.  The values VAL0,
+   * VAL1, etc are 24-bit values, in the lower 24 bits of their words.
+   * The upper 8 bits are 0.
+   */
+  VM_DEFINE_OP (67, abort, "abort", OP2 (U8_U24, X8_R24))
+#if 0
+    {
+      scm_t_uint32 tag, nvalues;
+
+      SCM_UNPACK_RTL_24 (op, tag);
+      SCM_UNPACK_RTL_24 (ip[1], nvalues);
+
+      SYNC_IP ();
+      vm_abort (vm, LOCAL_REF (tag), nvalues, &ip[2], &registers);
+
+      /* vm_abort should not return */
+      abort ();
+    }
+#else
+  abort();
+#endif
+
+  /* unwind _:24
+   *
+   * A normal exit from the dynamic extent of an expression. Pop the top
+   * entry off of the dynamic stack.
+   */
+  VM_DEFINE_OP (68, unwind, "unwind", OP1 (U8_X24))
+    {
+      scm_dynstack_pop (&current_thread->dynstack);
+      NEXT (1);
+    }
+
+  /* wind-fluids fluid-base:24 _:8 n:24 value0:24 0:8 ...
+   *
+   * Dynamically bind N fluids to values.  The fluids are expected to be
+   * allocated in a continguous range on the stack, starting from
+   * FLUID-BASE.  The values do not have this restriction.
+   */
+  VM_DEFINE_OP (69, wind_fluids, "wind-fluids", OP2 (U8_U24, X8_R24))
+#if 0
+    {
+      scm_t_uint32 fluid_base, n;
+
+      SCM_UNPACK_RTL_24 (op, fluid_base);
+      SCM_UNPACK_RTL_24 (ip[1], n);
+
+      scm_dynstack_push_fluids_shuffled (&current_thread->dynstack, n,
+                                         &fp[fluid_base], fp, &ip[2],
+                                         current_thread->dynamic_state);
+      NEXT (n + 2);
+    }
+#else
+  abort();
+#endif
+
+  /* unwind-fluids _:24
+   *
+   * Leave the dynamic extent of a with-fluids expression, restoring the
+   * fluids to their previous values.
+   */
+  VM_DEFINE_OP (70, unwind_fluids, "unwind-fluids", OP1 (U8_X24))
+    {
+      /* This function must not allocate.  */
+      scm_dynstack_unwind_fluids (&current_thread->dynstack,
+                                  current_thread->dynamic_state);
+      NEXT (1);
+    }
+
+  /* fluid-ref dst:12 src:12
+   *
+   * Reference the fluid in SRC, and place the value in DST.
+   */
+  VM_DEFINE_OP (71, fluid_ref, "fluid-ref", OP1 (U8_U12_U12) | OP_DST)
+    {
+      scm_t_uint16 dst, src;
+      size_t num;
+      SCM fluid, fluids;
+
+      SCM_UNPACK_RTL_12_12 (op, dst, src);
+      fluid = LOCAL_REF (src);
+      fluids = SCM_I_DYNAMIC_STATE_FLUIDS (current_thread->dynamic_state);
+      if (SCM_UNLIKELY (!SCM_FLUID_P (fluid))
+          || ((num = SCM_I_FLUID_NUM (fluid)) >= SCM_SIMPLE_VECTOR_LENGTH (fluids)))
+        {
+          /* Punt dynstate expansion and error handling to the C proc. */
+          SYNC_IP ();
+          LOCAL_SET (dst, scm_fluid_ref (fluid));
+        }
+      else
+        {
+          SCM val = SCM_SIMPLE_VECTOR_REF (fluids, num);
+          if (scm_is_eq (val, SCM_UNDEFINED))
+            val = SCM_I_FLUID_DEFAULT (fluid);
+          VM_ASSERT (!scm_is_eq (val, SCM_UNDEFINED),
+                     vm_error_unbound_fluid (program, fluid));
+          LOCAL_SET (dst, val);
+        }
+
+      NEXT (1);
+    }
+
+  /* fluid-set fluid:12 val:12
+   *
+   * Set the value of the fluid in DST to the value in SRC.
+   */
+  VM_DEFINE_OP (72, fluid_set, "fluid-set", OP1 (U8_U12_U12))
+    {
+      scm_t_uint16 a, b;
+      size_t num;
+      SCM fluid, fluids;
+
+      SCM_UNPACK_RTL_12_12 (op, a, b);
+      fluid = LOCAL_REF (a);
+      fluids = SCM_I_DYNAMIC_STATE_FLUIDS (current_thread->dynamic_state);
+      if (SCM_UNLIKELY (!SCM_FLUID_P (fluid))
+          || ((num = SCM_I_FLUID_NUM (fluid)) >= SCM_SIMPLE_VECTOR_LENGTH (fluids)))
+        {
+          /* Punt dynstate expansion and error handling to the C proc. */
+          SYNC_IP ();
+          scm_fluid_set_x (fluid, LOCAL_REF (b));
+        }
+      else
+        SCM_SIMPLE_VECTOR_SET (fluids, num, LOCAL_REF (b));
+
+      NEXT (1);
+    }
+
+
+  
+
+  /*
+   * Strings, symbols, and keywords
+   */
+
+  /* string-length dst:12 src:12
+   *
+   * Store the length of the string in SRC in DST.
+   */
+  VM_DEFINE_OP (73, string_length, "string-length", OP1 (U8_U12_U12) | OP_DST)
+    {
+      ARGS1 (str);
+      if (SCM_LIKELY (scm_is_string (str)))
+        RETURN (SCM_I_MAKINUM (scm_i_string_length (str)));
+      else
+        {
+          SYNC_IP ();
+          RETURN (scm_string_length (str));
+        }
+    }
+
+  /* string-ref dst:8 src:8 idx:8
+   *
+   * Fetch the character at position IDX in the string in SRC, and store
+   * it in DST.
+   */
+  VM_DEFINE_OP (74, string_ref, "string-ref", OP1 (U8_U8_U8_U8) | OP_DST)
+    {
+      scm_t_signed_bits i = 0;
+      ARGS2 (str, idx);
+      if (SCM_LIKELY (scm_is_string (str)
+                      && SCM_I_INUMP (idx)
+                      && ((i = SCM_I_INUM (idx)) >= 0)
+                      && i < scm_i_string_length (str)))
+        RETURN (SCM_MAKE_CHAR (scm_i_string_ref (str, i)));
+      else
+        {
+          SYNC_IP ();
+          RETURN (scm_string_ref (str, idx));
+        }
+    }
+
+  /* No string-set! instruction, as there is no good fast path there.  */
+
+  /* string-to-number dst:12 src:12
+   *
+   * Parse a string in SRC to a number, and store in DST.
+   */
+  VM_DEFINE_OP (75, string_to_number, "string->number", OP1 (U8_U12_U12) | OP_DST)
+    {
+      scm_t_uint16 dst, src;
+
+      SCM_UNPACK_RTL_12_12 (op, dst, src);
+      SYNC_IP ();
+      LOCAL_SET (dst,
+                 scm_string_to_number (LOCAL_REF (src),
+                                       SCM_UNDEFINED /* radix = 10 */));
+      NEXT (1);
+    }
+
+  /* string-to-symbol dst:12 src:12
+   *
+   * Parse a string in SRC to a symbol, and store in DST.
+   */
+  VM_DEFINE_OP (76, string_to_symbol, "string->symbol", OP1 (U8_U12_U12) | OP_DST)
+    {
+      scm_t_uint16 dst, src;
+
+      SCM_UNPACK_RTL_12_12 (op, dst, src);
+      SYNC_IP ();
+      LOCAL_SET (dst, scm_string_to_symbol (LOCAL_REF (src)));
+      NEXT (1);
+    }
+
+  /* symbol->keyword dst:12 src:12
+   *
+   * Make a keyword from the symbol in SRC, and store it in DST.
+   */
+  VM_DEFINE_OP (77, symbol_to_keyword, "symbol->keyword", OP1 (U8_U12_U12) | OP_DST)
+    {
+      scm_t_uint16 dst, src;
+      SCM_UNPACK_RTL_12_12 (op, dst, src);
+      SYNC_IP ();
+      LOCAL_SET (dst, scm_symbol_to_keyword (LOCAL_REF (src)));
+      NEXT (1);
+    }
+
+  
+
+  /*
+   * Pairs
+   */
+
+  /* cons dst:8 car:8 cdr:8
+   *
+   * Cons CAR and CDR, and store the result in DST.
+   */
+  VM_DEFINE_OP (78, cons, "cons", OP1 (U8_U8_U8_U8) | OP_DST)
+    {
+      ARGS2 (x, y);
+      RETURN (scm_cons (x, y));
+    }
+
+  /* car dst:12 src:12
+   *
+   * Place the car of SRC in DST.
+   */
+  VM_DEFINE_OP (79, car, "car", OP1 (U8_U12_U12) | OP_DST)
+    {
+      ARGS1 (x);
+      VM_VALIDATE_PAIR (x, "car");
+      RETURN (SCM_CAR (x));
+    }
+
+  /* cdr dst:12 src:12
+   *
+   * Place the cdr of SRC in DST.
+   */
+  VM_DEFINE_OP (80, cdr, "cdr", OP1 (U8_U12_U12) | OP_DST)
+    {
+      ARGS1 (x);
+      VM_VALIDATE_PAIR (x, "cdr");
+      RETURN (SCM_CDR (x));
+    }
+
+  /* set-car! pair:12 car:12
+   *
+   * Set the car of DST to SRC.
+   */
+  VM_DEFINE_OP (81, set_car, "set-car!", OP1 (U8_U12_U12))
+    {
+      scm_t_uint16 a, b;
+      SCM x, y;
+      SCM_UNPACK_RTL_12_12 (op, a, b);
+      x = LOCAL_REF (a);
+      y = LOCAL_REF (b);
+      VM_VALIDATE_PAIR (x, "set-car!");
+      SCM_SETCAR (x, y);
+      NEXT (1);
+    }
+
+  /* set-cdr! pair:12 cdr:12
+   *
+   * Set the cdr of DST to SRC.
+   */
+  VM_DEFINE_OP (82, set_cdr, "set-cdr!", OP1 (U8_U12_U12))
+    {
+      scm_t_uint16 a, b;
+      SCM x, y;
+      SCM_UNPACK_RTL_12_12 (op, a, b);
+      x = LOCAL_REF (a);
+      y = LOCAL_REF (b);
+      VM_VALIDATE_PAIR (x, "set-car!");
+      SCM_SETCDR (x, y);
+      NEXT (1);
+    }
+
+
+  
+
+  /*
+   * Numeric operations
+   */
+
+  /* add dst:8 a:8 b:8
+   *
+   * Add A to B, and place the result in DST.
+   */
+  VM_DEFINE_OP (83, add, "add", OP1 (U8_U8_U8_U8) | OP_DST)
+    {
+      BINARY_INTEGER_OP (+, scm_sum);
+    }
+
+  /* add1 dst:12 src:12
+   *
+   * Add 1 to the value in SRC, and place the result in DST.
+   */
+  VM_DEFINE_OP (84, add1, "add1", OP1 (U8_U12_U12) | OP_DST)
+    {
+      ARGS1 (x);
+
+      /* Check for overflow.  */
+      if (SCM_LIKELY ((scm_t_intptr) SCM_UNPACK (x) < INUM_MAX))
+        {
+          SCM result;
+
+          /* Add the integers without untagging.  */
+          result = SCM_PACK ((scm_t_intptr) SCM_UNPACK (x)
+                             + (scm_t_intptr) SCM_UNPACK (SCM_I_MAKINUM (1))
+                             - scm_tc2_int);
+
+          if (SCM_LIKELY (SCM_I_INUMP (result)))
+            RETURN (result);
+        }
+
+      SYNC_IP ();
+      RETURN (scm_sum (x, SCM_I_MAKINUM (1)));
+    }
+
+  /* sub dst:8 a:8 b:8
+   *
+   * Subtract B from A, and place the result in DST.
+   */
+  VM_DEFINE_OP (85, sub, "sub", OP1 (U8_U8_U8_U8) | OP_DST)
+    {
+      BINARY_INTEGER_OP (-, scm_difference);
+    }
+
+  /* sub1 dst:12 src:12
+   *
+   * Subtract 1 from SRC, and place the result in DST.
+   */
+  VM_DEFINE_OP (86, sub1, "sub1", OP1 (U8_U12_U12) | OP_DST)
+    {
+      ARGS1 (x);
+
+      /* Check for underflow.  */
+      if (SCM_LIKELY ((scm_t_intptr) SCM_UNPACK (x) > INUM_MIN))
+        {
+          SCM result;
+
+          /* Substract the integers without untagging.  */
+          result = SCM_PACK ((scm_t_intptr) SCM_UNPACK (x)
+                             - (scm_t_intptr) SCM_UNPACK (SCM_I_MAKINUM (1))
+                             + scm_tc2_int);
+
+          if (SCM_LIKELY (SCM_I_INUMP (result)))
+            RETURN (result);
+        }
+
+      SYNC_IP ();
+      RETURN (scm_difference (x, SCM_I_MAKINUM (1)));
+    }
+
+  /* mul dst:8 a:8 b:8
+   *
+   * Multiply A and B, and place the result in DST.
+   */
+  VM_DEFINE_OP (87, mul, "mul", OP1 (U8_U8_U8_U8) | OP_DST)
+    {
+      ARGS2 (x, y);
+      SYNC_IP ();
+      RETURN (scm_product (x, y));
+    }
+
+  /* div dst:8 a:8 b:8
+   *
+   * Divide A by B, and place the result in DST.
+   */
+  VM_DEFINE_OP (88, div, "div", OP1 (U8_U8_U8_U8) | OP_DST)
+    {
+      ARGS2 (x, y);
+      SYNC_IP ();
+      RETURN (scm_divide (x, y));
+    }
+
+  /* quo dst:8 a:8 b:8
+   *
+   * Divide A by B, and place the quotient in DST.
+   */
+  VM_DEFINE_OP (89, quo, "quo", OP1 (U8_U8_U8_U8) | OP_DST)
+    {
+      ARGS2 (x, y);
+      SYNC_IP ();
+      RETURN (scm_quotient (x, y));
+    }
+
+  /* rem dst:8 a:8 b:8
+   *
+   * Divide A by B, and place the remainder in DST.
+   */
+  VM_DEFINE_OP (90, rem, "rem", OP1 (U8_U8_U8_U8) | OP_DST)
+    {
+      ARGS2 (x, y);
+      SYNC_IP ();
+      RETURN (scm_remainder (x, y));
+    }
+
+  /* mod dst:8 a:8 b:8
+   *
+   * Place the modulo of A by B in DST.
+   */
+  VM_DEFINE_OP (91, mod, "mod", OP1 (U8_U8_U8_U8) | OP_DST)
+    {
+      ARGS2 (x, y);
+      SYNC_IP ();
+      RETURN (scm_modulo (x, y));
+    }
+
+  /* ash dst:8 a:8 b:8
+   *
+   * Shift A arithmetically by B bits, and place the result in DST.
+   */
+  VM_DEFINE_OP (92, ash, "ash", OP1 (U8_U8_U8_U8) | OP_DST)
+    {
+      ARGS2 (x, y);
+      if (SCM_I_INUMP (x) && SCM_I_INUMP (y))
+        {
+          if (SCM_I_INUM (y) < 0)
+            /* Right shift, will be a fixnum. */
+            RETURN (SCM_I_MAKINUM (SCM_I_INUM (x) >> -SCM_I_INUM (y)));
+          else
+            /* Left shift. See comments in scm_ash. */
+            {
+              scm_t_signed_bits nn, bits_to_shift;
+
+              nn = SCM_I_INUM (x);
+              bits_to_shift = SCM_I_INUM (y);
+
+              if (bits_to_shift < SCM_I_FIXNUM_BIT-1
+                  && ((scm_t_bits)
+                      (SCM_SRS (nn, (SCM_I_FIXNUM_BIT-1 - bits_to_shift)) + 1)
+                      <= 1))
+                RETURN (SCM_I_MAKINUM (nn << bits_to_shift));
+              /* fall through */
+            }
+          /* fall through */
+        }
+      SYNC_IP ();
+      RETURN (scm_ash (x, y));
+    }
+
+  /* logand dst:8 a:8 b:8
+   *
+   * Place the bitwise AND of A and B into DST.
+   */
+  VM_DEFINE_OP (93, logand, "logand", OP1 (U8_U8_U8_U8) | OP_DST)
+    {
+      ARGS2 (x, y);
+      if (SCM_I_INUMP (x) && SCM_I_INUMP (y))
+        RETURN (SCM_I_MAKINUM (SCM_I_INUM (x) & SCM_I_INUM (y)));
+      SYNC_IP ();
+      RETURN (scm_logand (x, y));
+    }
+
+  /* logior dst:8 a:8 b:8
+   *
+   * Place the bitwise inclusive OR of A with B in DST.
+   */
+  VM_DEFINE_OP (94, logior, "logior", OP1 (U8_U8_U8_U8) | OP_DST)
+    {
+      ARGS2 (x, y);
+      if (SCM_I_INUMP (x) && SCM_I_INUMP (y))
+        RETURN (SCM_I_MAKINUM (SCM_I_INUM (x) | SCM_I_INUM (y)));
+      SYNC_IP ();
+      RETURN (scm_logior (x, y));
+    }
+
+  /* logxor dst:8 a:8 b:8
+   *
+   * Place the bitwise exclusive OR of A with B in DST.
+   */
+  VM_DEFINE_OP (95, logxor, "logxor", OP1 (U8_U8_U8_U8) | OP_DST)
+    {
+      ARGS2 (x, y);
+      if (SCM_I_INUMP (x) && SCM_I_INUMP (y))
+        RETURN (SCM_I_MAKINUM (SCM_I_INUM (x) ^ SCM_I_INUM (y)));
+      SYNC_IP ();
+      RETURN (scm_logxor (x, y));
+    }
+
+  /* vector-length dst:12 src:12
+   *
+   * Store the length of the vector in SRC in DST.
+   */
+  VM_DEFINE_OP (96, vector_length, "vector-length", OP1 (U8_U12_U12) | OP_DST)
+    {
+      ARGS1 (vect);
+      if (SCM_LIKELY (SCM_I_IS_VECTOR (vect)))
+        RETURN (SCM_I_MAKINUM (SCM_I_VECTOR_LENGTH (vect)));
+      else
+        {
+          SYNC_IP ();
+          RETURN (scm_vector_length (vect));
+        }
+    }
+
+  /* vector-ref dst:8 src:8 idx:8
+   *
+   * Fetch the item at position IDX in the vector in SRC, and store it
+   * in DST.
+   */
+  VM_DEFINE_OP (97, vector_ref, "vector-ref", OP1 (U8_U8_U8_U8) | OP_DST)
+    {
+      scm_t_signed_bits i = 0;
+      ARGS2 (vect, idx);
+      if (SCM_LIKELY (SCM_I_IS_NONWEAK_VECTOR (vect)
+                      && SCM_I_INUMP (idx)
+                      && ((i = SCM_I_INUM (idx)) >= 0)
+                      && i < SCM_I_VECTOR_LENGTH (vect)))
+        RETURN (SCM_I_VECTOR_ELTS (vect)[i]);
+      else
+        {
+          SYNC_IP ();
+          RETURN (scm_vector_ref (vect, idx));
+        }
+    }
+
+  /* constant-vector-ref dst:8 src:8 idx:8
+   *
+   * Fill DST with the item IDX elements into the vector at SRC.  Useful
+   * for building data types using vectors.
+   */
+  VM_DEFINE_OP (98, constant_vector_ref, "constant-vector-ref", OP1 (U8_U8_U8_U8) | OP_DST)
+    {
+      scm_t_uint8 dst, src, idx;
+      SCM v;
+      
+      SCM_UNPACK_RTL_8_8_8 (op, dst, src, idx);
+      v = LOCAL_REF (src);
+      if (SCM_LIKELY (SCM_I_IS_NONWEAK_VECTOR (v)
+                      && idx < SCM_I_VECTOR_LENGTH (v)))
+        LOCAL_SET (dst, SCM_I_VECTOR_ELTS (LOCAL_REF (src))[idx]);
+      else
+        LOCAL_SET (dst, scm_c_vector_ref (v, idx));
+      NEXT (1);
+    }
+
+  /* vector-set! dst:8 idx:8 src:8
+   *
+   * Store SRC into the vector DST at index IDX.
+   */
+  VM_DEFINE_OP (99, vector_set, "vector-set", OP1 (U8_U8_U8_U8))
+    {
+      scm_t_uint8 dst, idx_var, src;
+      SCM vect, idx, val;
+      scm_t_signed_bits i = 0;
+
+      SCM_UNPACK_RTL_8_8_8 (op, dst, idx_var, src);
+      vect = LOCAL_REF (dst);
+      idx = LOCAL_REF (idx_var);
+      val = LOCAL_REF (src);
+
+      if (SCM_LIKELY (SCM_I_IS_NONWEAK_VECTOR (vect)
+                      && SCM_I_INUMP (idx)
+                      && ((i = SCM_I_INUM (idx)) >= 0)
+                      && i < SCM_I_VECTOR_LENGTH (vect)))
+        SCM_I_VECTOR_WELTS (vect)[i] = val;
+      else
+        {
+          SYNC_IP ();
+          scm_vector_set_x (vect, idx, val);
+        }
+      NEXT (1);
+    }
+
+
+  
+
+  /*
+   * Structs and GOOPS
+   */
+
+  /* struct-vtable dst:12 src:12
+   *
+   * Store the vtable of SRC into DST.
+   */
+  VM_DEFINE_OP (100, struct_vtable, "struct-vtable", OP1 (U8_U12_U12) | OP_DST)
+    {
+      ARGS1 (obj);
+      VM_VALIDATE_STRUCT (obj, "struct_vtable");
+      RETURN (SCM_STRUCT_VTABLE (obj));
+    }
+
+  /* make-struct dst:12 vtable:12 _:8 n-init:24 init0:24 0:8 ...
+   *
+   * Make a new struct with VTABLE, and place it in DST.  The struct
+   * will be constructed with N-INIT initializers, which are located in
+   * the locals given by INIT0....  The format of INIT0... is as in the
+   * "call" opcode: unsigned 24-bit values, with 0 in the high byte.
+   */
+  VM_DEFINE_OP (101, make_struct, "make-struct", OP2 (U8_U12_U12, X8_R24))
+#if 0
+    {
+      scm_t_uint16 dst, vtable_r;
+      scm_t_uint32 n_init, n;
+      SCM vtable, ret;
+
+      SCM_UNPACK_RTL_12_12 (op, dst, vtable_r);
+      vtable = LOCAL_REF (vtable_r);
+      SCM_UNPACK_RTL_24 (ip[1], n_init);
+
+      SYNC_IP ();
+
+      if (SCM_LIKELY (SCM_STRUCTP (vtable)
+                      && SCM_VTABLE_FLAG_IS_SET (vtable, SCM_VTABLE_FLAG_SIMPLE)
+                      && (SCM_STRUCT_DATA_REF (vtable, scm_vtable_index_size)
+                          == n_init)
+                      && !SCM_VTABLE_INSTANCE_FINALIZER (vtable)))
+        {
+          /* Verily, we are making a simple struct with the right number of
+             initializers, and no finalizer. */
+          ret = scm_words ((scm_t_bits)SCM_STRUCT_DATA (vtable) | scm_tc3_struct,
+                           n_init + 2);
+          SCM_SET_CELL_WORD_1 (ret, (scm_t_bits)SCM_CELL_OBJECT_LOC (ret, 2));
+          
+          for (n = 0; n < n_init; n++)
+            SCM_STRUCT_DATA (ret)[n] = SCM_UNPACK (LOCAL_REF (ip[n + 1]));
+        }
+      else
+        ret = scm_c_make_structvs (vtable, fp, &ip[1], n_init);
+
+      LOCAL_SET (dst, ret);
+      NEXT (n_init + 1);
+    }
+#else
+  abort ();
+#endif
+
+  /* struct-ref dst:8 src:8 idx:8
+   *
+   * Fetch the item at slot IDX in the struct in SRC, and store it
+   * in DST.
+   */
+  VM_DEFINE_OP (102, struct_ref, "struct-ref", OP1 (U8_U8_U8_U8) | OP_DST)
+    {
+      ARGS2 (obj, pos);
+
+      if (SCM_LIKELY (SCM_STRUCTP (obj)
+                      && SCM_STRUCT_VTABLE_FLAG_IS_SET (obj,
+                                                        SCM_VTABLE_FLAG_SIMPLE)
+                      && SCM_I_INUMP (pos)))
+        {
+          SCM vtable;
+          scm_t_bits index, len;
+
+          /* True, an inum is a signed value, but cast to unsigned it will
+             certainly be more than the length, so we will fall through if
+             index is negative. */
+          index = SCM_I_INUM (pos);
+          vtable = SCM_STRUCT_VTABLE (obj);
+          len = SCM_STRUCT_DATA_REF (vtable, scm_vtable_index_size);
+
+          if (SCM_LIKELY (index < len))
+            {
+              scm_t_bits *data = SCM_STRUCT_DATA (obj);
+              RETURN (SCM_PACK (data[index]));
+            }
+        }
+
+      SYNC_IP ();
+      RETURN (scm_struct_ref (obj, pos));
+    }
+
+  /* struct-set! dst:8 idx:8 src:8
+   *
+   * Store SRC into the struct DST at slot IDX.
+   */
+  VM_DEFINE_OP (103, struct_set, "struct-set!", OP1 (U8_U8_U8_U8))
+    {
+      scm_t_uint8 dst, idx, src;
+      SCM obj, pos, val;
+      
+      SCM_UNPACK_RTL_8_8_8 (op, dst, idx, src);
+      obj = LOCAL_REF (dst);
+      pos = LOCAL_REF (idx);
+      val = LOCAL_REF (src);
+      
+      if (SCM_LIKELY (SCM_STRUCTP (obj)
+                      && SCM_STRUCT_VTABLE_FLAG_IS_SET (obj,
+                                                        SCM_VTABLE_FLAG_SIMPLE)
+                      && SCM_STRUCT_VTABLE_FLAG_IS_SET (obj,
+                                                        SCM_VTABLE_FLAG_SIMPLE_RW)
+                      && SCM_I_INUMP (pos)))
+        {
+          SCM vtable;
+          scm_t_bits index, len;
+
+          /* See above regarding index being >= 0. */
+          index = SCM_I_INUM (pos);
+          vtable = SCM_STRUCT_VTABLE (obj);
+          len = SCM_STRUCT_DATA_REF (vtable, scm_vtable_index_size);
+          if (SCM_LIKELY (index < len))
+            {
+              scm_t_bits *data = SCM_STRUCT_DATA (obj);
+              data[index] = SCM_UNPACK (val);
+              NEXT (1);
+            }
+        }
+
+      SYNC_IP ();
+      scm_struct_set_x (obj, pos, val);
+      NEXT (1);
+    }
+
+  /* class-of dst:12 type:12
+   *
+   * Store the vtable of SRC into DST.
+   */
+  VM_DEFINE_OP (104, class_of, "class-of", OP1 (U8_U12_U12) | OP_DST)
+    {
+      ARGS1 (obj);
+      if (SCM_INSTANCEP (obj))
+        RETURN (SCM_CLASS_OF (obj));
+      SYNC_IP ();
+      RETURN (scm_class_of (obj));
+    }
+
+  /* slot-ref dst:8 src:8 idx:8
+   *
+   * Fetch the item at slot IDX in the struct in SRC, and store it in
+   * DST.  Unlike struct-ref, IDX is an 8-bit immediate value, not an
+   * index into the stack.
+   */
+  VM_DEFINE_OP (105, slot_ref, "slot-ref", OP1 (U8_U8_U8_U8) | OP_DST)
+    {
+      scm_t_uint8 dst, src, idx;
+      SCM_UNPACK_RTL_8_8_8 (op, dst, src, idx);
+      LOCAL_SET (dst,
+                 SCM_PACK (SCM_STRUCT_DATA (LOCAL_REF (src))[idx]));
+      NEXT (1);
+    }
+
+  /* slot-set! dst:8 idx:8 src:8
+   *
+   * Store SRC into slot IDX of the struct in DST.  Unlike struct-set!,
+   * IDX is an 8-bit immediate value, not an index into the stack.
+   */
+  VM_DEFINE_OP (106, slot_set, "slot-set!", OP1 (U8_U8_U8_U8))
+    {
+      scm_t_uint8 dst, idx, src;
+      SCM_UNPACK_RTL_8_8_8 (op, dst, idx, src);
+      SCM_STRUCT_DATA (LOCAL_REF (dst))[idx] = SCM_UNPACK (LOCAL_REF (src));
+      NEXT (1);
+    }
+
+
+  
+
+  /*
+   * Arrays, packed uniform arrays, and bytevectors.
+   */
+
+  /* load-typed-array dst:8 type:8 shape:8 offset:32 len:32
+   *
+   * Load the contiguous typed array located at OFFSET 32-bit words away
+   * from the instruction pointer, and store into DST.  LEN is a byte
+   * length.  OFFSET is signed.
+   */
+  VM_DEFINE_OP (107, load_typed_array, "load-typed-array", OP3 (U8_U8_U8_U8, N32, U32) | OP_DST)
+    {
+      scm_t_uint8 dst, type, shape;
+      scm_t_int32 offset;
+      scm_t_uint32 len;
+
+      SCM_UNPACK_RTL_8_8_8 (op, dst, type, shape);
+      offset = ip[1];
+      len = ip[2];
+      SYNC_IP ();
+      LOCAL_SET (dst, scm_from_contiguous_typed_array (LOCAL_REF (type),
+                                                       LOCAL_REF (shape),
+                                                       ip + offset, len));
+      NEXT (3);
+    }
+
+  /* make-array dst:12 type:12 _:8 fill:12 bounds:12
+   *
+   * Make a new array with TYPE, FILL, and BOUNDS, storing it in DST.
+   */
+  VM_DEFINE_OP (108, make_array, "make-array", OP2 (U8_U12_U12, X8_U12_U12) | OP_DST)
+    {
+      scm_t_uint16 dst, type, fill, bounds;
+      SCM_UNPACK_RTL_12_12 (op, dst, type);
+      SCM_UNPACK_RTL_12_12 (ip[1], fill, bounds);
+      SYNC_IP ();
+      LOCAL_SET (dst, scm_make_typed_array (LOCAL_REF (type), LOCAL_REF (fill),
+                                            LOCAL_REF (bounds)));
+      NEXT (2);
+    }
+
+  /* bv-u8-ref dst:8 src:8 idx:8
+   * bv-s8-ref dst:8 src:8 idx:8
+   * bv-u16-ref dst:8 src:8 idx:8
+   * bv-s16-ref dst:8 src:8 idx:8
+   * bv-u32-ref dst:8 src:8 idx:8
+   * bv-s32-ref dst:8 src:8 idx:8
+   * bv-u64-ref dst:8 src:8 idx:8
+   * bv-s64-ref dst:8 src:8 idx:8
+   * bv-f32-ref dst:8 src:8 idx:8
+   * bv-f64-ref dst:8 src:8 idx:8
+   *
+   * Fetch the item at byte offset IDX in the bytevector SRC, and store
+   * it in DST.  All accesses use native endianness.
+   */
+#define BV_FIXABLE_INT_REF(stem, fn_stem, type, size)			\
+  do {									\
+    scm_t_signed_bits i;                                                \
+    const scm_t_ ## type *int_ptr;					\
+    ARGS2 (bv, idx);							\
+									\
+    VM_VALIDATE_BYTEVECTOR (bv, "bv-" #stem "-ref");                    \
+    i = SCM_I_INUM (idx);                                               \
+    int_ptr = (scm_t_ ## type *) (SCM_BYTEVECTOR_CONTENTS (bv) + i);	\
+									\
+    if (SCM_LIKELY (SCM_I_INUMP (idx)					\
+                    && (i >= 0)						\
+                    && (i + size <= SCM_BYTEVECTOR_LENGTH (bv))		\
+                    && (ALIGNED_P (int_ptr, scm_t_ ## type))))		\
+      RETURN (SCM_I_MAKINUM (*int_ptr));                                \
+    else                                                                \
+      {									\
+        SYNC_IP ();							\
+        RETURN (scm_bytevector_ ## fn_stem ## _ref (bv, idx));		\
+      }									\
+  } while (0)
+
+#define BV_INT_REF(stem, type, size)					\
+  do {									\
+    scm_t_signed_bits i;                                                \
+    const scm_t_ ## type *int_ptr;					\
+    ARGS2 (bv, idx);							\
+									\
+    VM_VALIDATE_BYTEVECTOR (bv, "bv-" #stem "-ref");                    \
+    i = SCM_I_INUM (idx);                                               \
+    int_ptr = (scm_t_ ## type *) (SCM_BYTEVECTOR_CONTENTS (bv) + i);	\
+									\
+    if (SCM_LIKELY (SCM_I_INUMP (idx)					\
+                    && (i >= 0)						\
+                    && (i + size <= SCM_BYTEVECTOR_LENGTH (bv))		\
+                    && (ALIGNED_P (int_ptr, scm_t_ ## type))))		\
+      {									\
+        scm_t_ ## type x = *int_ptr;					\
+        if (SCM_FIXABLE (x))						\
+          RETURN (SCM_I_MAKINUM (x));					\
+        else								\
+          {								\
+            SYNC_IP ();                                                 \
+            RETURN (scm_from_ ## type (x));				\
+          }								\
+      }									\
+    else                                                                \
+      {									\
+        SYNC_IP ();							\
+        RETURN (scm_bytevector_ ## stem ## _native_ref (bv, idx));	\
+      }									\
+  } while (0)
+
+#define BV_FLOAT_REF(stem, fn_stem, type, size)				\
+  do {									\
+    scm_t_signed_bits i;                                                \
+    const type *float_ptr;						\
+    ARGS2 (bv, idx);							\
+									\
+    VM_VALIDATE_BYTEVECTOR (bv, "bv-" #stem "-ref");                    \
+    i = SCM_I_INUM (idx);                                               \
+    float_ptr = (type *) (SCM_BYTEVECTOR_CONTENTS (bv) + i);		\
+									\
+    SYNC_IP ();                                                         \
+    if (SCM_LIKELY (SCM_I_INUMP (idx)					\
+                    && (i >= 0)						\
+                    && (i + size <= SCM_BYTEVECTOR_LENGTH (bv))		\
+                    && (ALIGNED_P (float_ptr, type))))			\
+      RETURN (scm_from_double (*float_ptr));				\
+    else                                                                \
+      RETURN (scm_bytevector_ ## fn_stem ## _native_ref (bv, idx));	\
+  } while (0)
+
+  VM_DEFINE_OP (109, bv_u8_ref, "bv-u8-ref", OP1 (U8_U8_U8_U8) | OP_DST)
+    BV_FIXABLE_INT_REF (u8, u8, uint8, 1);
+
+  VM_DEFINE_OP (110, bv_s8_ref, "bv-s8-ref", OP1 (U8_U8_U8_U8) | OP_DST)
+    BV_FIXABLE_INT_REF (s8, s8, int8, 1);
+
+  VM_DEFINE_OP (111, bv_u16_ref, "bv-u16-ref", OP1 (U8_U8_U8_U8) | OP_DST)
+    BV_FIXABLE_INT_REF (u16, u16_native, uint16, 2);
+
+  VM_DEFINE_OP (112, bv_s16_ref, "bv-s16-ref", OP1 (U8_U8_U8_U8) | OP_DST)
+    BV_FIXABLE_INT_REF (s16, s16_native, int16, 2);
+
+  VM_DEFINE_OP (113, bv_u32_ref, "bv-u32-ref", OP1 (U8_U8_U8_U8) | OP_DST)
+#if SIZEOF_VOID_P > 4
+    BV_FIXABLE_INT_REF (u32, u32_native, uint32, 4);
+#else
+    BV_INT_REF (u32, uint32, 4);
+#endif
+
+  VM_DEFINE_OP (114, bv_s32_ref, "bv-s32-ref", OP1 (U8_U8_U8_U8) | OP_DST)
+#if SIZEOF_VOID_P > 4
+    BV_FIXABLE_INT_REF (s32, s32_native, int32, 4);
+#else
+    BV_INT_REF (s32, int32, 4);
+#endif
+
+  VM_DEFINE_OP (115, bv_u64_ref, "bv-u64-ref", OP1 (U8_U8_U8_U8) | OP_DST)
+    BV_INT_REF (u64, uint64, 8);
+
+  VM_DEFINE_OP (116, bv_s64_ref, "bv-s64-ref", OP1 (U8_U8_U8_U8) | OP_DST)
+    BV_INT_REF (s64, int64, 8);
+
+  VM_DEFINE_OP (117, bv_f32_ref, "bv-f32-ref", OP1 (U8_U8_U8_U8) | OP_DST)
+    BV_FLOAT_REF (f32, ieee_single, float, 4);
+
+  VM_DEFINE_OP (118, bv_f64_ref, "bv-f64-ref", OP1 (U8_U8_U8_U8) | OP_DST)
+    BV_FLOAT_REF (f64, ieee_double, double, 8);
+
+  /* bv-u8-set! dst:8 idx:8 src:8
+   * bv-s8-set! dst:8 idx:8 src:8
+   * bv-u16-set! dst:8 idx:8 src:8
+   * bv-s16-set! dst:8 idx:8 src:8
+   * bv-u32-set! dst:8 idx:8 src:8
+   * bv-s32-set! dst:8 idx:8 src:8
+   * bv-u64-set! dst:8 idx:8 src:8
+   * bv-s64-set! dst:8 idx:8 src:8
+   * bv-f32-set! dst:8 idx:8 src:8
+   * bv-f64-set! dst:8 idx:8 src:8
+   *
+   * Store SRC into the bytevector DST at byte offset IDX.  Multibyte
+   * values are written using native endianness.
+   */
+#define BV_FIXABLE_INT_SET(stem, fn_stem, type, min, max, size)		\
+  do {									\
+    scm_t_uint8 dst, idx, src;                                          \
+    scm_t_signed_bits i, j = 0;                                         \
+    SCM bv, scm_idx, val;                                               \
+    scm_t_ ## type *int_ptr;						\
+									\
+    SCM_UNPACK_RTL_8_8_8 (op, dst, idx, src);                           \
+    bv = LOCAL_REF (dst);                                               \
+    scm_idx = LOCAL_REF (idx);                                          \
+    val = LOCAL_REF (src);                                              \
+    VM_VALIDATE_BYTEVECTOR (bv, "bv-" #stem "-set");                    \
+    i = SCM_I_INUM (scm_idx);                                           \
+    int_ptr = (scm_t_ ## type *) (SCM_BYTEVECTOR_CONTENTS (bv) + i);	\
+									\
+    if (SCM_LIKELY (SCM_I_INUMP (scm_idx)                               \
+                    && (i >= 0)                                         \
+                    && (i + size <= SCM_BYTEVECTOR_LENGTH (bv))         \
+                    && (ALIGNED_P (int_ptr, scm_t_ ## type))		\
+                    && (SCM_I_INUMP (val))				\
+                    && ((j = SCM_I_INUM (val)) >= min)                  \
+                    && (j <= max)))					\
+      *int_ptr = (scm_t_ ## type) j;					\
+    else                                                                \
+      {                                                                 \
+        SYNC_IP ();                                                     \
+        scm_bytevector_ ## fn_stem ## _set_x (bv, scm_idx, val);        \
+      }                                                                 \
+    NEXT (1);                                                           \
+  } while (0)
+
+#define BV_INT_SET(stem, type, size)					\
+  do {									\
+    scm_t_uint8 dst, idx, src;                                          \
+    scm_t_signed_bits i;                                                \
+    SCM bv, scm_idx, val;                                               \
+    scm_t_ ## type *int_ptr;						\
+									\
+    SCM_UNPACK_RTL_8_8_8 (op, dst, idx, src);                           \
+    bv = LOCAL_REF (dst);                                               \
+    scm_idx = LOCAL_REF (idx);                                          \
+    val = LOCAL_REF (src);                                              \
+    VM_VALIDATE_BYTEVECTOR (bv, "bv-" #stem "-set");                    \
+    i = SCM_I_INUM (scm_idx);                                           \
+    int_ptr = (scm_t_ ## type *) (SCM_BYTEVECTOR_CONTENTS (bv) + i);	\
+									\
+    if (SCM_LIKELY (SCM_I_INUMP (scm_idx)                               \
+                    && (i >= 0)                                         \
+                    && (i + size <= SCM_BYTEVECTOR_LENGTH (bv))         \
+                    && (ALIGNED_P (int_ptr, scm_t_ ## type))))          \
+      *int_ptr = scm_to_ ## type (val);                                 \
+    else                                                                \
+      {                                                                 \
+        SYNC_IP ();                                                     \
+        scm_bytevector_ ## stem ## _native_set_x (bv, scm_idx, val);    \
+      }                                                                 \
+    NEXT (1);                                                           \
+  } while (0)
+
+#define BV_FLOAT_SET(stem, fn_stem, type, size)                         \
+  do {                                                                  \
+    scm_t_uint8 dst, idx, src;                                          \
+    scm_t_signed_bits i;                                                \
+    SCM bv, scm_idx, val;                                               \
+    type *float_ptr;                                                    \
+									\
+    SCM_UNPACK_RTL_8_8_8 (op, dst, idx, src);                           \
+    bv = LOCAL_REF (dst);                                               \
+    scm_idx = LOCAL_REF (idx);                                          \
+    val = LOCAL_REF (src);                                              \
+    VM_VALIDATE_BYTEVECTOR (bv, "bv-" #stem "-set");                    \
+    i = SCM_I_INUM (scm_idx);                                           \
+    float_ptr = (type *) (SCM_BYTEVECTOR_CONTENTS (bv) + i);            \
+                                                                        \
+    if (SCM_LIKELY (SCM_I_INUMP (scm_idx)                               \
+                    && (i >= 0)                                         \
+                    && (i + size <= SCM_BYTEVECTOR_LENGTH (bv))         \
+                    && (ALIGNED_P (float_ptr, type))))                  \
+      *float_ptr = scm_to_double (val);                                 \
+    else                                                                \
+      {                                                                 \
+        SYNC_IP ();                                                     \
+        scm_bytevector_ ## fn_stem ## _native_set_x (bv, scm_idx, val); \
+      }                                                                 \
+    NEXT (1);                                                           \
+  } while (0)
+
+  VM_DEFINE_OP (119, bv_u8_set, "bv-u8-set!", OP1 (U8_U8_U8_U8))
+    BV_FIXABLE_INT_SET (u8, u8, uint8, 0, SCM_T_UINT8_MAX, 1);
+
+  VM_DEFINE_OP (120, bv_s8_set, "bv-s8-set!", OP1 (U8_U8_U8_U8))
+    BV_FIXABLE_INT_SET (s8, s8, int8, SCM_T_INT8_MIN, SCM_T_INT8_MAX, 1);
+
+  VM_DEFINE_OP (121, bv_u16_set, "bv-u16-set!", OP1 (U8_U8_U8_U8))
+    BV_FIXABLE_INT_SET (u16, u16_native, uint16, 0, SCM_T_UINT16_MAX, 2);
+
+  VM_DEFINE_OP (122, bv_s16_set, "bv-s16-set!", OP1 (U8_U8_U8_U8))
+    BV_FIXABLE_INT_SET (s16, s16_native, int16, SCM_T_INT16_MIN, SCM_T_INT16_MAX, 2);
+
+  VM_DEFINE_OP (123, bv_u32_set, "bv-u32-set!", OP1 (U8_U8_U8_U8))
+#if SIZEOF_VOID_P > 4
+    BV_FIXABLE_INT_SET (u32, u32_native, uint32, 0, SCM_T_UINT32_MAX, 4);
+#else
+    BV_INT_SET (u32, uint32, 4);
+#endif
+
+  VM_DEFINE_OP (124, bv_s32_set, "bv-s32-set!", OP1 (U8_U8_U8_U8))
+#if SIZEOF_VOID_P > 4
+    BV_FIXABLE_INT_SET (s32, s32_native, int32, SCM_T_INT32_MIN, SCM_T_INT32_MAX, 4);
+#else
+    BV_INT_SET (s32, int32, 4);
+#endif
+
+  VM_DEFINE_OP (125, bv_u64_set, "bv-u64-set!", OP1 (U8_U8_U8_U8))
+    BV_INT_SET (u64, uint64, 8);
+
+  VM_DEFINE_OP (126, bv_s64_set, "bv-s64-set!", OP1 (U8_U8_U8_U8))
+    BV_INT_SET (s64, int64, 8);
+
+  VM_DEFINE_OP (127, bv_f32_set, "bv-f32-set!", OP1 (U8_U8_U8_U8))
+    BV_FLOAT_SET (f32, ieee_single, float, 4);
+
+  VM_DEFINE_OP (128, bv_f64_set, "bv-f64-set!", OP1 (U8_U8_U8_U8))
+    BV_FLOAT_SET (f64, ieee_double, double, 8);
+
+  END_DISPATCH_SWITCH;
+
+ vm_error_bad_instruction:
+  vm_error_bad_instruction (op);
+
+  abort (); /* never reached */
+}
+
+
+#undef ABORT_CONTINUATION_HOOK
+#undef ALIGNED_P
+#undef APPLY_HOOK
+#undef ARGS1
+#undef ARGS2
+#undef BEGIN_DISPATCH_SWITCH
+#undef BINARY_INTEGER_OP
+#undef BR_ARITHMETIC
+#undef BR_BINARY
+#undef BR_NARGS
+#undef BR_UNARY
+#undef BV_FIXABLE_INT_REF
+#undef BV_FIXABLE_INT_SET
+#undef BV_FLOAT_REF
+#undef BV_FLOAT_SET
+#undef BV_INT_REF
+#undef BV_INT_SET
+#undef CACHE_REGISTER
+#undef CHECK_OVERFLOW
+#undef END_DISPATCH_SWITCH
+#undef FREE_VARIABLE_REF
+#undef INIT
+#undef INUM_MAX
+#undef INUM_MIN
+#undef LOCAL_REF
+#undef LOCAL_SET
+#undef NEXT
+#undef NEXT_HOOK
+#undef NEXT_JUMP
+#undef POP_CONTINUATION_HOOK
+#undef PUSH_CONTINUATION_HOOK
+#undef RESTORE_CONTINUATION_HOOK
+#undef RETURN
+#undef RETURN_ONE_VALUE
+#undef RETURN_VALUE_LIST
 #undef RUN_HOOK
-#undef RUN_HOOK1
+#undef RUN_HOOK0
 #undef SYNC_ALL
 #undef SYNC_BEFORE_GC
 #undef SYNC_IP
@@ -459,11 +3603,29 @@ VM_NAME (SCM vm, SCM program, SCM *argv, int nargs)
 #undef VARIABLE_BOUNDP
 #undef VARIABLE_REF
 #undef VARIABLE_SET
+#undef VM_CHECK_FREE_VARIABLE
+#undef VM_CHECK_OBJECT
+#undef VM_CHECK_UNDERFLOW
 #undef VM_DEFINE_OP
 #undef VM_INSTRUCTION_TO_LABEL
 #undef VM_USE_HOOKS
+#undef VM_VALIDATE_BYTEVECTOR
+#undef VM_VALIDATE_PAIR
+#undef VM_VALIDATE_STRUCT
 
 /*
+(defun renumber-ops ()
+  "start from top of buffer and renumber 'VM_DEFINE_FOO (\n' sequences"
+  (interactive "")
+  (save-excursion
+    (let ((counter -1)) (goto-char (point-min))
+      (while (re-search-forward "^ *VM_DEFINE_[^ ]+ (\\([^,]+\\)," (point-max) t)
+        (replace-match
+         (number-to-string (setq counter (1+ counter)))
+          t t nil 1)))))
+(renumber-ops)
+*/
+/*
   Local Variables:
   c-file-style: "gnu"
   End:
diff --git a/libguile/vm.c b/libguile/vm.c
index cbef0d979..f43191299 100644
--- a/libguile/vm.c
+++ b/libguile/vm.c
@@ -594,6 +594,30 @@ vm_error_bad_wide_string_length (size_t len)
 
 static SCM boot_continuation;
 
+static SCM rtl_boot_continuation;
+static SCM rtl_apply;
+static SCM rtl_values;
+
+static const scm_t_uint32 rtl_boot_continuation_code[] = {
+  SCM_PACK_RTL_24 (scm_rtl_op_halt_values, 0), /* empty stack frame in r0-r2, results from r3 */
+  SCM_PACK_RTL_24 (scm_rtl_op_halt, 0) /* result in r0 */
+};
+
+static scm_t_uint32* rtl_boot_multiple_value_continuation_code =
+  (scm_t_uint32 *) rtl_boot_continuation_code;
+
+static scm_t_uint32* rtl_boot_single_value_continuation_code =
+  (scm_t_uint32 *) rtl_boot_continuation_code + 1;
+
+static const scm_t_uint32 rtl_apply_code[] = {
+  SCM_PACK_RTL_24 (scm_rtl_op_apply, 0) /* proc in r0, args from r1, nargs set */
+};
+
+static const scm_t_uint32 rtl_values_code[] = {
+  SCM_PACK_RTL_24 (scm_rtl_op_values, 0) /* vals from r0 */
+};
+
+
 
 /*
  * VM
@@ -637,18 +661,22 @@ initialize_default_stack_size (void)
 }
 
 #define VM_NAME   vm_regular_engine
+#define RTL_VM_NAME   rtl_vm_regular_engine
 #define FUNC_NAME "vm-regular-engine"
 #define VM_ENGINE SCM_VM_REGULAR_ENGINE
 #include "vm-engine.c"
 #undef VM_NAME
+#undef RTL_VM_NAME
 #undef FUNC_NAME
 #undef VM_ENGINE
 
 #define VM_NAME	  vm_debug_engine
+#define RTL_VM_NAME   rtl_vm_debug_engine
 #define FUNC_NAME "vm-debug-engine"
 #define VM_ENGINE SCM_VM_DEBUG_ENGINE
 #include "vm-engine.c"
 #undef VM_NAME
+#undef RTL_VM_NAME
 #undef FUNC_NAME
 #undef VM_ENGINE
 
@@ -1110,6 +1138,10 @@ scm_init_vm (void)
 #ifndef SCM_MAGIC_SNARFER
 #include "libguile/vm.x"
 #endif
+
+  rtl_boot_continuation = scm_i_make_rtl_program (rtl_boot_continuation_code);
+  rtl_apply = scm_i_make_rtl_program (rtl_apply_code);
+  rtl_values = scm_i_make_rtl_program (rtl_values_code);
 }
 
 /*
diff --git a/module/system/vm/instruction.scm b/module/system/vm/instruction.scm
index 287e47293..81c6ab5b9 100644
--- a/module/system/vm/instruction.scm
+++ b/module/system/vm/instruction.scm
@@ -1,6 +1,6 @@
 ;;; Guile VM instructions
 
-;; Copyright (C) 2001, 2010 Free Software Foundation, Inc.
+;; Copyright (C) 2001, 2010, 2012 Free Software Foundation, Inc.
 
 ;;; This library is free software; you can redistribute it and/or
 ;;; modify it under the terms of the GNU Lesser General Public
@@ -19,7 +19,8 @@
 ;;; Code:
 
 (define-module (system vm instruction)
-  #:export (instruction-list
+  #:export (rtl-instruction-list
+            instruction-list
            instruction? instruction-length
            instruction-pops instruction-pushes
            instruction->opcode opcode->instruction))
diff --git a/module/system/vm/program.scm b/module/system/vm/program.scm
index 1d0100180..187509313 100644
--- a/module/system/vm/program.scm
+++ b/module/system/vm/program.scm
@@ -26,6 +26,7 @@
   #:use-module (srfi srfi-1)
   #:use-module (srfi srfi-26)
   #:export (make-program
+            make-rtl-program
 
             make-binding binding:name binding:boxed? binding:index
             binding:start binding:end
@@ -43,6 +44,7 @@
 
             program-meta
             program-objcode program? program-objects
+            rtl-program? rtl-program-code
             program-module program-base
             program-free-variables
             program-num-free-variables