Silence the transforms that detect rightward arithmetic shift

[sbcl.git] / src / compiler / srctran.lisp

diff --git a/src/compiler/srctran.lisp b/src/compiler/srctran.lisp
index c1aa106..e13c30e 100644 (file)
--- a/src/compiler/srctran.lisp
+++ b/src/compiler/srctran.lisp
@@ -2771,8 +2771,13 @@
   (defun %ash/right (integer amount)
     (ash integer (- amount)))
 
-  (deftransform ash ((integer amount) (sb!vm:signed-word (integer * 0)))
+  (deftransform ash ((integer amount))
     "Convert ASH of signed word to %ASH/RIGHT"
+    (unless (and (csubtypep (lvar-type integer) ; do that ourselves to avoid
+                            (specifier-type 'sb!vm:signed-word)) ; optimization
+                 (csubtypep (lvar-type amount)  ; notes.
+                            (specifier-type '(integer * 0))))
+      (give-up-ir1-transform))
     (when (constant-lvar-p amount)
       (give-up-ir1-transform))
     (let ((use (lvar-uses amount)))
@@ -2789,8 +2794,13 @@
                                       ,(1- sb!vm:n-word-bits)
                                       (- amount)))))))
 
-  (deftransform ash ((integer amount) (word (integer * 0)))
+  (deftransform ash ((integer amount))
     "Convert ASH of word to %ASH/RIGHT"
+    (unless (and (csubtypep (lvar-type integer)
+                            (specifier-type 'sb!vm:word))
+                 (csubtypep (lvar-type amount)
+                            (specifier-type '(integer * 0))))
+      (give-up-ir1-transform))
     (when (constant-lvar-p amount)
       (give-up-ir1-transform))
     (let ((use (lvar-uses amount)))
@@ -3401,14 +3411,17 @@
   (def logxor -1 (lognot x))
   (def logxor 0 x))
 
+(defun least-zero-bit (x)
+  (and (/= x -1)
+       (1- (integer-length (logxor x (1+ x))))))
+
 (deftransform logand ((x y) (* (constant-arg t)) *)
   "fold identity operation"
-  (let ((y (lvar-value y)))
-    (unless (and (plusp y)
-                 (= y (1- (ash 1 (integer-length y)))))
-      (give-up-ir1-transform))
-    (unless (csubtypep (lvar-type x)
-                       (specifier-type `(integer 0 ,y)))
+  (let* ((y (lvar-value y))
+         (width (or (least-zero-bit y) '*)))
+    (unless (and (neq width 0) ; (logand x 0) handled elsewhere
+                 (csubtypep (lvar-type x)
+                            (specifier-type `(unsigned-byte ,width))))
       (give-up-ir1-transform))
     'x))
 
@@ -3419,6 +3432,16 @@
       (give-up-ir1-transform))
     'x))
 
+(deftransform logior ((x y) (* (constant-arg t)) *)
+  "fold identity operation"
+  (let* ((y (lvar-value y))
+         (width (or (least-zero-bit (lognot y))
+                    (give-up-ir1-transform)))) ; (logior x 0) handled elsewhere
+    (unless (csubtypep (lvar-type x)
+                       (specifier-type `(integer ,(- (ash 1 width)) -1)))
+      (give-up-ir1-transform))
+    'x))
+
 ;;; Pick off easy association opportunities for constant folding.
 ;;; More complicated stuff that also depends on commutativity
 ;;; (e.g. (f (f x k1) (f y k2)) => (f (f x y) (f k1 k2))) should
@@ -3444,13 +3467,17 @@
                   (splice-fun-args x ',folded 2)
                   `(lambda (x y z)
                      (declare (ignore y z))
-                     (,',operator x ',(,folded y (lvar-value z))))))))
+                     ;; (operator (folded x y) z)
+                     ;; == (operator x (folded z y))
+                     (,',operator x ',(,folded (lvar-value z) y)))))))
   (def logand)
   (def logior)
   (def logxor)
   (def logtest :folded logand)
   (def + :type rational)
-  (def * :type rational))
+  (def + :type rational :folded -)
+  (def * :type rational)
+  (def * :type rational :folded /))
 
 (deftransform mask-signed-field ((width x) ((constant-arg unsigned-byte) *))
   "Fold mask-signed-field/mask-signed-field of constant width"