Add sign-extending make-immediate instruction

* doc/ref/vm.texi (Instruction Set, Constant Instructions): Document new
  instruction.
* libguile/instructions.c (FOR_EACH_INSTRUCTION_WORD_TYPE): New first
  word kind with zi16 operand.
* libguile/jit.c (compile_make_immediate, compile_make_immediate_slow):
  New compilers.
  (COMPILE_X8_S8_ZI16): New operand kind.
* libguile/vm-engine.c (make-immediate): New instruction.
* module/language/bytecode.scm:
* module/system/vm/assembler.scm (encode-X8_S8_ZI16<-/shuffle):
  (signed-bits, load-constant): Support the new instruction kind.
* module/system/vm/disassembler.scm (disassemblers)
  (sign-extended-immediate, code-annotation): Support for zi16
  operands.

1 files changed, 8 insertions, 2 deletions

diff --git a/doc/ref/vm.texi b/doc/ref/vm.texi
index a94c60576..5064532e2 100644
--- a/doc/ref/vm.texi
+++ b/doc/ref/vm.texi
@@ -579,10 +579,12 @@ An unsigned @var{n}-bit integer, indicating a constant value.
 @item l24
 An offset from the current @code{ip}, in 32-bit units, as a signed
 24-bit value.  Indicates a bytecode address, for a relative jump.
-@item i16
+@item zi16
+@itemx i16
 @itemx i32
 An immediate Scheme value (@pxref{Immediate Objects}), encoded directly
-in 16 or 32 bits.
+in 16 or 32 bits.  @code{zi16} is sign-extended; the others are
+zero-extended.
 @item a32
 @itemx b32
 An immediate Scheme value, encoded as a pair of 32-bit words.
@@ -1358,6 +1360,10 @@ two kinds.
 The first set of instructions loads immediate values.  These
 instructions encode the immediate directly into the instruction stream.
 
+@deftypefn Instruction {} make-immediate s8:@var{dst} zi16:@var{low-bits}
+Make an immediate whose low bits are @var{low-bits}, sign-extended.
+@end deftypefn
+
 @deftypefn Instruction {} make-short-immediate s8:@var{dst} i16:@var{low-bits}
 Make an immediate whose low bits are @var{low-bits}, and whose top bits are
 0.