X-Git-Url: http://repo.macrolet.net/gitweb/?a=blobdiff_plain;f=src%2Fcode%2Floop.lisp;h=9ffa2c0b55e48f21d42134ea408fc834f31cdd32;hb=b1a20dc4dee1a14c9b11eabf4130187227b9b2a7;hp=68f1741f44306e03cbd66e8edbd98ad45ee69585;hpb=4898ef32c639b1c7f4ee13a5ba566ce6debd03e6;p=sbcl.git

diff --git a/src/code/loop.lisp b/src/code/loop.lisp
index 68f1741..9ffa2c0 100644
--- a/src/code/loop.lisp
+++ b/src/code/loop.lisp
@@ -503,27 +503,21 @@ code to be loaded.
 ;;;; code analysis stuff
 
 (defun loop-constant-fold-if-possible (form &optional expected-type)
-  (let ((new-form form) (constantp nil) (constant-value nil))
-    (when (setq constantp (constantp new-form))
-      (setq constant-value (eval new-form)))
+  (let* ((constantp (sb!xc:constantp form))
+         (value (and constantp (sb!int:constant-form-value form))))
     (when (and constantp expected-type)
-      (unless (sb!xc:typep constant-value expected-type)
+      (unless (sb!xc:typep value expected-type)
         (loop-warn "~@<The form ~S evaluated to ~S, which was not of ~
                     the anticipated type ~S.~:@>"
-                   form constant-value expected-type)
-        (setq constantp nil constant-value nil)))
-    (values new-form constantp constant-value)))
-
-(defun loop-constantp (form)
-  (constantp form))
+                   form value expected-type)
+        (setq constantp nil value nil)))
+    (values form constantp value)))
 
 ;;;; LOOP iteration optimization
 
-(defvar *loop-duplicate-code*
-        nil)
+(defvar *loop-duplicate-code* nil)
 
-(defvar *loop-iteration-flag-var*
-        (make-symbol "LOOP-NOT-FIRST-TIME"))
+(defvar *loop-iteration-flag-var* (make-symbol "LOOP-NOT-FIRST-TIME"))
 
 (defun loop-code-duplication-threshold (env)
   (declare (ignore env))
@@ -1067,7 +1061,7 @@ code to be loaded.
         (t (error "invalid LOOP variable passed in: ~S" name))))
 
 (defun loop-maybe-bind-form (form data-type)
-  (if (loop-constantp form)
+  (if (constantp form)
       form
       (loop-make-var (gensym "LOOP-BIND-") form data-type)))
 
@@ -1795,6 +1789,27 @@ code to be loaded.
          (setq step-hack
                `(,variable ,step-hack)))
        (let ((first-test test) (remaining-tests test))
+         ;; As far as I can tell, the effect of the following code is
+         ;; to detect cases where we know statically whether the first
+         ;; iteration of the loop will be executed. Depending on the
+         ;; situation, we can either:
+         ;;  a) save one jump and one comparison per loop (not per iteration)
+         ;;     when it will get executed
+         ;;  b) remove the loop body completely when it won't be executed
+         ;;
+         ;; Noble goals. However, the code generated in case a) will
+         ;; fool the loop induction variable detection, and cause
+         ;; code like (LOOP FOR I TO 10 ...) to use generic addition
+         ;; (bug #278a).
+         ;;
+         ;; Since the gain in case a) is rather minimal and Python is
+         ;; generally smart enough to handle b) without any extra
+         ;; support from the loop macro, I've disabled this code for
+         ;; now. The code and the comment left here in case somebody
+         ;; extends the induction variable bound detection to work
+         ;; with code where the stepping precedes the test.
+         ;; -- JES 2005-11-30
+         #+nil
          (when (and stepby-constantp start-constantp limit-constantp
                     (realp start-value) (realp limit-value))
            (when (setq first-test
@@ -1815,22 +1830,6 @@ code to be loaded.
     '((:from :upfrom :downfrom) (:to :upto :downto :above :below) (:by))
     nil (list (list kwd val)))))
 
-(defun loop-sequence-elements-path (variable data-type prep-phrases
-                                    &key
-                                    fetch-function
-                                    size-function
-                                    sequence-type
-                                    element-type)
-  (multiple-value-bind (indexv) (loop-named-var 'index)
-    (let ((sequencev (loop-named-var 'sequence)))
-      (list* nil nil                            ; dummy bindings and prologue
-             (loop-sequencer
-              indexv 'fixnum
-              variable (or data-type element-type)
-              sequencev sequence-type
-              `(,fetch-function ,sequencev ,indexv)
-              `(,size-function ,sequencev)
-              prep-phrases)))))
 
 ;;;; builtin LOOP iteration paths