actually implement "fixing letrec"

* module/Makefile.am (SOURCES): Reorganize so GHIL is compiled last,
  along with ecmascript.

* module/language/scheme/spec.scm: Remove references to GHIL, as it's
  bitrotten and obsolete..

* module/language/tree-il.scm (make-tree-il-folder): Rework so that we
  only have down and up procs, and call down and up on each element.
* module/language/tree-il/analyze.scm (analyze-lexicals): Fix a thinko
  handling let-values.

* module/language/tree-il/fix-letrec.scm: Actually implement fixing
  letrec. The resulting code will perform better, but violations of the
  letrec restriction are not detected. This behavior is allowed by the
  spec, but it is undesirable. Perhaps that will be fixed later.

* module/language/tree-il/inline.scm (inline!): Fix a case in which
  ((lambda args foo)) would be erroneously inlined to foo. Remove empty
  let, letrec, and fix statements.

* module/language/tree-il/primitives.scm (effect-free-primitive?): New
  public predicate.

7 files changed, 252 insertions, 82 deletions

diff --git a/module/Makefile.am b/module/Makefile.am
index f3b7e62d5..5eec063c2 100644
--- a/module/Makefile.am
+++ b/module/Makefile.am
@@ -37,11 +37,11 @@ SOURCES =								\
   system/base/message.scm						\
 									\
   language/tree-il.scm							\
-  language/ghil.scm language/glil.scm language/assembly.scm		\
+  language/glil.scm language/assembly.scm				\
 									\
   $(SCHEME_LANG_SOURCES) 						\
   $(TREE_IL_LANG_SOURCES)						\
-  $(GHIL_LANG_SOURCES) $(GLIL_LANG_SOURCES)				\
+  $(GLIL_LANG_SOURCES)							\
   $(ASSEMBLY_LANG_SOURCES) $(BYTECODE_LANG_SOURCES)			\
   $(OBJCODE_LANG_SOURCES) $(VALUE_LANG_SOURCES)				\
 									\
@@ -50,9 +50,10 @@ SOURCES =								\
   $(RNRS_SOURCES)							\
   $(OOP_SOURCES)							\
   $(SYSTEM_SOURCES)                                                     \
+  $(SCRIPTS_SOURCES)                                                    \
+  $(GHIL_LANG_SOURCES)                                                  \
   $(ECMASCRIPT_LANG_SOURCES)						\
-  $(BRAINFUCK_LANG_SOURCES)						\
-  $(SCRIPTS_SOURCES)
+  $(BRAINFUCK_LANG_SOURCES)
 
 ## test.scm is not currently installed.
 EXTRA_DIST += ice-9/test.scm ice-9/compile-psyntax.scm ice-9/ChangeLog-2008
@@ -83,8 +84,8 @@ TREE_IL_LANG_SOURCES =						\
   language/tree-il/compile-glil.scm 				\
   language/tree-il/spec.scm
 
-GHIL_LANG_SOURCES =					\
-  language/ghil/spec.scm language/ghil/compile-glil.scm
+GHIL_LANG_SOURCES =						\
+  language/ghil.scm language/ghil/spec.scm language/ghil/compile-glil.scm
 
 GLIL_LANG_SOURCES =						\
   language/glil/spec.scm language/glil/compile-assembly.scm 	\
diff --git a/module/language/scheme/spec.scm b/module/language/scheme/spec.scm
index 21aa023a5..df618581f 100644
--- a/module/language/scheme/spec.scm
+++ b/module/language/scheme/spec.scm
@@ -1,6 +1,6 @@
 ;;; Guile Scheme specification
 
-;; Copyright (C) 2001 Free Software Foundation, Inc.
+;; Copyright (C) 2001, 2009 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
@@ -20,7 +20,6 @@
 
 (define-module (language scheme spec)
   #:use-module (system base language)
-  #:use-module (language scheme compile-ghil)
   #:use-module (language scheme compile-tree-il)
   #:use-module (language scheme decompile-tree-il)
   #:export (scheme))
@@ -39,8 +38,7 @@
   #:title	"Guile Scheme"
   #:version	"0.5"
   #:reader	read
-  #:compilers   `((tree-il . ,compile-tree-il)
-                  (ghil . ,compile-ghil))
+  #:compilers   `((tree-il . ,compile-tree-il))
   #:decompilers `((tree-il . ,decompile-tree-il))
   #:evaluator	(lambda (x module) (primitive-eval x))
   #:printer	write
diff --git a/module/language/tree-il.scm b/module/language/tree-il.scm
index 8ad7065c6..ad8b73176 100644
--- a/module/language/tree-il.scm
+++ b/module/language/tree-il.scm
@@ -327,73 +327,51 @@ This is an implementation of `foldts' as described by Andy Wingo in
 (define-syntax make-tree-il-folder
   (syntax-rules ()
     ((_ seed ...)
-     (lambda (tree down up leaf seed ...)
+     (lambda (tree down up seed ...)
        (define (fold-values proc exps seed ...)
          (if (null? exps)
              (values seed ...)
              (let-values (((seed ...) (proc (car exps) seed ...)))
                (fold-values proc (cdr exps) seed ...))))
        (let foldts ((tree tree) (seed seed) ...)
-         (record-case tree
-           ((<lexical-set> exp)
-            (let*-values (((seed ...) (down tree seed ...))
-                          ((seed ...) (foldts exp seed ...)))
-              (up tree seed ...)))
-           ((<module-set> exp)
-            (let*-values (((seed ...) (down tree seed ...))
-                          ((seed ...) (foldts exp seed ...)))
-              (up tree seed ...)))
-           ((<toplevel-set> exp)
-            (let*-values (((seed ...) (down tree seed ...))
-                          ((seed ...) (foldts exp seed ...)))
-              (up tree seed ...)))
-           ((<toplevel-define> exp)
-            (let*-values (((seed ...) (down tree seed ...))
-                          ((seed ...) (foldts exp seed ...)))
-              (up tree seed ...)))
-           ((<conditional> test then else)
-            (let*-values (((seed ...) (down tree seed ...))
-                          ((seed ...) (foldts test seed ...))
-                          ((seed ...) (foldts then seed ...))
-                          ((seed ...) (foldts else seed ...)))
-              (up tree seed ...)))
-           ((<application> proc args)
-            (let*-values (((seed ...) (down tree seed ...))
-                          ((seed ...) (foldts proc seed ...))
-                          ((seed ...) (fold-values foldts args seed ...)))
-              (up tree seed ...)))
-           ((<sequence> exps)
-            (let*-values (((seed ...) (down tree seed ...))
-                          ((seed ...) (fold-values foldts exps seed ...)))
-              (up tree seed ...)))
-           ((<lambda> body)
-            (let*-values (((seed ...) (down tree seed ...))
-                          ((seed ...) (foldts body seed ...)))
-              (up tree seed ...)))
-           ((<let> vals body)
-            (let*-values (((seed ...) (down tree seed ...))
-                          ((seed ...) (fold-values foldts vals seed ...))
-                          ((seed ...) (foldts body seed ...)))
-              (up tree seed ...)))
-           ((<letrec> vals body)
-            (let*-values (((seed ...) (down tree seed ...))
-                          ((seed ...) (fold-values foldts vals seed ...))
-                          ((seed ...) (foldts body seed ...)))
-              (up tree seed ...)))
-
-           ((<fix> vals body)
-            (let*-values (((seed ...) (down tree seed ...))
-                          ((seed ...) (fold-values foldts vals seed ...))
-                          ((seed ...) (foldts body seed ...)))
-              (up tree seed ...)))
-           ((<let-values> exp body)
-            (let*-values (((seed ...) (down tree seed ...))
-                          ((seed ...) (fold-values foldts vals seed ...))
-                          ((seed ...) (foldts body seed ...)))
-              (up tree seed ...)))
-           (else
-            (leaf tree seed ...))))))))
-
+         (let*-values
+             (((seed ...) (down tree seed ...))
+              ((seed ...)
+               (record-case tree
+                 ((<lexical-set> exp)
+                  (foldts exp seed ...))
+                 ((<module-set> exp)
+                  (foldts exp seed ...))
+                 ((<toplevel-set> exp)
+                  (foldts exp seed ...))
+                 ((<toplevel-define> exp)
+                  (foldts exp seed ...))
+                 ((<conditional> test then else)
+                  (let*-values (((seed ...) (foldts test seed ...))
+                                ((seed ...) (foldts then seed ...)))
+                    (foldts else seed ...)))
+                 ((<application> proc args)
+                  (let-values (((seed ...) (foldts proc seed ...)))
+                    (fold-values foldts args seed ...)))
+                 ((<sequence> exps)
+                  (fold-values foldts exps seed ...))
+                 ((<lambda> body)
+                  (foldts body seed ...))
+                 ((<let> vals body)
+                  (let*-values (((seed ...) (fold-values foldts vals seed ...)))
+                    (foldts body seed ...)))
+                 ((<letrec> vals body)
+                  (let*-values (((seed ...) (fold-values foldts vals seed ...)))
+                    (foldts body seed ...)))
+                 ((<fix> vals body)
+                  (let*-values (((seed ...) (fold-values foldts vals seed ...)))
+                    (foldts body seed ...)))
+                 ((<let-values> exp body)
+                  (let*-values (((seed ...) (foldts exp seed ...)))
+                    (foldts body seed ...)))
+                 (else
+                  (values seed ...)))))
+           (up tree seed ...)))))))
 
 (define (post-order! f x)
   (let lp ((x x))
diff --git a/module/language/tree-il/analyze.scm b/module/language/tree-il/analyze.scm
index 73ef8ba21..49633aa28 100644
--- a/module/language/tree-il/analyze.scm
+++ b/module/language/tree-il/analyze.scm
@@ -319,13 +319,12 @@
              ;; the 1+ for this var
              (max nmax (allocate! body proc (1+ n))))
             (else               
-             (let ((v (if (pair? vars) (car vars) vars)))
-               (let ((v (car vars)))
-                 (hashq-set!
-                  allocation v
-                  (make-hashq proc
-                              `(#t ,(hashq-ref assigned v) . ,n)))
-                 (lp (cdr vars) (1+ n)))))))))
+             (let ((v (car vars)))
+               (hashq-set!
+                allocation v
+                (make-hashq proc
+                            `(#t ,(hashq-ref assigned v) . ,n)))
+               (lp (cdr vars) (1+ n))))))))
       
       (else n)))
 
diff --git a/module/language/tree-il/fix-letrec.scm b/module/language/tree-il/fix-letrec.scm
index 61504f6f1..0ed7b6bab 100644
--- a/module/language/tree-il/fix-letrec.scm
+++ b/module/language/tree-il/fix-letrec.scm
@@ -18,12 +18,163 @@
 
 (define-module (language tree-il fix-letrec)
   #:use-module (system base syntax)
+  #:use-module (srfi srfi-1)
+  #:use-module (srfi srfi-11)
   #:use-module (language tree-il)
+  #:use-module (language tree-il primitives)
   #:export (fix-letrec!))
 
 ;; For a detailed discussion, see "Fixing Letrec: A Faithful Yet
 ;; Efficient Implementation of Scheme’s Recursive Binding Construct", by
 ;; Oscar Waddell, Dipanwita Sarkar, and R. Kent Dybvig.
 
+(define fix-fold
+  (make-tree-il-folder unref ref set simple lambda complex))
+
+(define (simple-expression? x bound-vars)
+  (record-case x
+    ((<void>) #t)
+    ((<const>) #t)
+    ((<lexical-ref> gensym)
+     (not (memq gensym bound-vars)))
+    ((<conditional> test then else)
+     (and (simple-expression? test bound-vars)
+          (simple-expression? then bound-vars)
+          (simple-expression? else bound-vars)))
+    ((<sequence> exps)
+     (and-map (lambda (x) (simple-expression? x bound-vars))
+              exps))
+    ((<application> proc args)
+     (and (primitive-ref? proc)
+          (effect-free-primitive? (primitive-ref-name proc))
+          (and-map (lambda (x) (simple-expression? x bound-vars))
+                   args)))
+    (else #f)))
+
+(define (partition-vars x)
+  (let-values
+      (((unref ref set simple lambda* complex)
+        (fix-fold x
+                  (lambda (x unref ref set simple lambda* complex)
+                    (record-case x
+                      ((<lexical-ref> gensym)
+                       (values (delq gensym unref)
+                               (lset-adjoin eq? ref gensym)
+                               set
+                               simple
+                               lambda*
+                               complex))
+                      ((<lexical-set> gensym)
+                       (values unref
+                               ref
+                               (lset-adjoin eq? set gensym)
+                               simple
+                               lambda*
+                               complex))
+                      ((<letrec> vars)
+                       (values (append vars unref)
+                               ref
+                               set
+                               simple
+                               lambda*
+                               complex))
+                      (else
+                       (values unref ref set simple lambda* complex))))
+                  (lambda (x unref ref set simple lambda* complex)
+                    (record-case x
+                      ((<letrec> (orig-vars vars) vals)
+                       (let lp ((vars orig-vars) (vals vals)
+                                (s '()) (l '()) (c '()))
+                         (cond
+                          ((null? vars)
+                           (values unref
+                                   ref
+                                   set
+                                   (append s simple)
+                                   (append l lambda*)
+                                   (append c complex)))
+                          ((memq (car vars) unref)
+                           (lp (cdr vars) (cdr vals)
+                               s l c))
+                          ((memq (car vars) set)
+                           (lp (cdr vars) (cdr vals)
+                               s l (cons (car vars) c)))
+                          ((lambda? (car vals))
+                           (lp (cdr vars) (cdr vals)
+                               s (cons (car vars) l) c))
+                          ((simple-expression? (car vals) orig-vars)
+                           (lp (cdr vars) (cdr vals)
+                               (cons (car vars) s) l c))
+                          (else
+                           (lp (cdr vars) (cdr vals)
+                               s l (cons (car vars) c))))))
+                      (else
+                       (values unref ref set simple lambda* complex))))
+                  '()
+                  '()
+                  '()
+                  '()
+                  '()
+                  '())))
+    (values unref simple lambda* complex)))
+
 (define (fix-letrec! x)
-  x)
+  (let-values (((unref simple lambda* complex) (partition-vars x)))
+    (post-order!
+     (lambda (x)
+       (record-case x
+
+         ;; Sets to unreferenced variables may be replaced by their
+         ;; expression, called for effect.
+         ((<lexical-set> gensym exp)
+          (if (memq gensym unref)
+              (make-sequence #f (list (make-void #f) exp))
+              x))
+
+         ((<letrec> src names vars vals body)
+          (let ((binds (map list vars names vals)))
+            (define (lookup set)
+              (map (lambda (v) (assq v binds))
+                   (lset-intersection eq? vars set)))
+            (let ((u (lookup unref))
+                  (s (lookup simple))
+                  (l (lookup lambda*))
+                  (c (lookup complex)))
+              ;; Bind "simple" bindings, and locations for complex
+              ;; bindings.
+              (make-let
+               src
+               (append (map cadr s) (map cadr c))
+               (append (map car s) (map car c))
+               (append (map caddr s) (map (lambda (x) (make-void #f)) c))
+               ;; Bind lambdas using the fixpoint operator.
+               (make-fix
+                src (map cadr l) (map car l) (map caddr l)
+                (make-sequence
+                 src
+                 (append
+                  ;; The right-hand-sides of the unreferenced
+                  ;; bindings, for effect.
+                  (map caddr u)
+                  (if (null? c)
+                      ;; No complex bindings, just emit the body.
+                      (list body)
+                      (list
+                       ;; Evaluate the the "complex" bindings, in a `let' to
+                       ;; indicate that order doesn't matter, and bind to
+                       ;; their variables.
+                       (let ((tmps (map (lambda (x) (gensym)) c)))
+                         (make-let
+                          #f (map cadr c) tmps (map caddr c)
+                          (make-sequence
+                           #f
+                           (map (lambda (x tmp)
+                                  (make-lexical-set
+                                   #f (cadr x) (car x)
+                                   (make-lexical-ref #f (cadr x) tmp)))
+                                c tmps))))
+                       ;; Finally, the body.
+                       body)))))))))
+
+         (else x)))
+     x)))
diff --git a/module/language/tree-il/inline.scm b/module/language/tree-il/inline.scm
index fd3fbc921..adc3f18bd 100644
--- a/module/language/tree-il/inline.scm
+++ b/module/language/tree-il/inline.scm
@@ -41,7 +41,8 @@
         (cond
 
          ;; ((lambda () x)) => x
-         ((and (lambda? proc) (null? args))
+         ((and (lambda? proc) (null? (lambda-vars proc))
+               (null? args))
           (lambda-body proc))
 
          ;; (call-with-values (lambda () foo) (lambda (a b . c) bar))
@@ -66,6 +67,15 @@
                              (lambda-body consumer))))
 
          (else #f)))
-
+       
+       ((<let> vars body)
+        (if (null? vars) body x))
+       
+       ((<letrec> vars body)
+        (if (null? vars) body x))
+       
+       ((<fix> vars body)
+        (if (null? vars) body x))
+       
        (else #f)))
    x))
diff --git a/module/language/tree-il/primitives.scm b/module/language/tree-il/primitives.scm
index 0f58e22fb..24900c64d 100644
--- a/module/language/tree-il/primitives.scm
+++ b/module/language/tree-il/primitives.scm
@@ -25,7 +25,7 @@
   #:use-module (language tree-il)
   #:use-module (srfi srfi-16)
   #:export (resolve-primitives! add-interesting-primitive!
-            expand-primitives!))
+            expand-primitives! effect-free-primitive?))
 
 (define *interesting-primitive-names* 
   '(apply @apply
@@ -85,6 +85,39 @@
 
 (for-each add-interesting-primitive! *interesting-primitive-names*)
 
+(define *effect-free-primitives*
+  '(values
+    eq? eqv? equal?
+    = < > <= >= zero?
+    + * - / 1- 1+ quotient remainder modulo
+    not
+    pair? null? list? acons cons cons*
+    list vector
+    car cdr
+    caar cadr cdar cddr
+    caaar caadr cadar caddr cdaar cdadr cddar cdddr
+    caaaar caaadr caadar caaddr cadaar cadadr caddar cadddr
+    cdaaar cdaadr cdadar cdaddr cddaar cddadr cdddar cddddr
+    vector-ref
+    bytevector-u8-ref bytevector-s8-ref
+    bytevector-u16-ref bytevector-u16-native-ref
+    bytevector-s16-ref bytevector-s16-native-ref
+    bytevector-u32-ref bytevector-u32-native-ref
+    bytevector-s32-ref bytevector-s32-native-ref
+    bytevector-u64-ref bytevector-u64-native-ref
+    bytevector-s64-ref bytevector-s64-native-ref
+    bytevector-ieee-single-ref bytevector-ieee-single-native-ref
+    bytevector-ieee-double-ref bytevector-ieee-double-native-ref))
+
+
+(define *effect-free-primitive-table* (make-hash-table))
+
+(for-each (lambda (x) (hashq-set! *effect-free-primitive-table* x #t))
+          *effect-free-primitives*)
+
+(define (effect-free-primitive? prim)
+  (hashq-ref *effect-free-primitive-table* prim))
+
 (define (resolve-primitives! x mod)
   (post-order!
    (lambda (x)