X-Git-Url: http://repo.macrolet.net/gitweb/?a=blobdiff_plain;f=src%2Fcompiler%2Fsparc%2Farith.lisp;h=412c56faef4a146c6188aef6b0c5657dc4bcf20c;hb=85c1cf858999279da6f4f470c4f3c582ad9f2dbf;hp=331a70960656faae3488af8b4f24cf76af88521b;hpb=58c1c5751bc1ed21dad031349108e969ab88c52d;p=sbcl.git

diff --git a/src/compiler/sparc/arith.lisp b/src/compiler/sparc/arith.lisp
index 331a709..412c56f 100644
--- a/src/compiler/sparc/arith.lisp
+++ b/src/compiler/sparc/arith.lisp
@@ -111,68 +111,75 @@
 
 (eval-when (:compile-toplevel :load-toplevel :execute)
 
-(defmacro define-binop (translate untagged-penalty op)
+(defmacro define-binop (translate untagged-penalty op
+			&optional arg-swap restore-fixnum-mask)
   `(progn
-     (define-vop (,(symbolicate "FAST-" translate "/FIXNUM=>FIXNUM")
+     (define-vop (,(symbolicate 'fast translate '/fixnum=>fixnum)
 		  fast-fixnum-binop)
+       ,@(when restore-fixnum-mask
+	   `((:temporary (:sc non-descriptor-reg) temp)))
        (:translate ,translate)
        (:generator 2
-	 (inst ,op r x y)))
-     (define-vop (,(symbolicate 'fast- translate '-c/fixnum=>fixnum)
-		  fast-fixnum-binop-c)
-       (:translate ,translate)
-       (:generator 1
-	 (inst ,op r x (fixnumize y))))
-     (define-vop (,(symbolicate "FAST-" translate "/SIGNED=>SIGNED")
+	 ,(if arg-swap
+	      `(inst ,op ,(if restore-fixnum-mask 'temp 'r) y x)
+	      `(inst ,op ,(if restore-fixnum-mask 'temp 'r) x y))
+	 ,@(when restore-fixnum-mask
+	     `((inst andn r temp fixnum-tag-mask)))))
+     ,@(unless arg-swap
+	 `((define-vop (,(symbolicate 'fast- translate '-c/fixnum=>fixnum)
+			fast-fixnum-binop-c)
+	     ,@(when restore-fixnum-mask
+		 `((:temporary (:sc non-descriptor-reg) temp)))
+	     (:translate ,translate)
+	     (:generator 1
+	       (inst ,op ,(if restore-fixnum-mask 'temp 'r) x (fixnumize y))
+	       ,@(when restore-fixnum-mask
+		   `((inst andn r temp fixnum-tag-mask)))))))
+     (define-vop (,(symbolicate 'fast- translate '/signed=>signed)
 		  fast-signed-binop)
        (:translate ,translate)
        (:generator ,(1+ untagged-penalty)
-	 (inst ,op r x y)))
-     (define-vop (,(symbolicate 'fast- translate '-c/signed=>signed)
-		  fast-signed-binop-c)
-       (:translate ,translate)
-       (:generator ,untagged-penalty
-	 (inst ,op r x y)))
-     (define-vop (,(symbolicate "FAST-" translate "/UNSIGNED=>UNSIGNED")
+	 ,(if arg-swap
+	      `(inst ,op r y x)
+	      `(inst ,op r x y))))
+     ,@(unless arg-swap
+	 `((define-vop (,(symbolicate 'fast- translate '-c/signed=>signed)
+			fast-signed-binop-c)
+	     (:translate ,translate)
+	     (:generator ,untagged-penalty
+	       (inst ,op r x y)))))
+     (define-vop (,(symbolicate 'fast- translate '/unsigned=>unsigned)
 		  fast-unsigned-binop)
        (:translate ,translate)
        (:generator ,(1+ untagged-penalty)
-	 (inst ,op r x y)))
-     (define-vop (,(symbolicate 'fast- translate '-c/unsigned=>unsigned)
-		  fast-unsigned-binop-c)
-       (:translate ,translate)
-       (:generator ,untagged-penalty
-	 (inst ,op r x y)))))
+	 ,(if arg-swap
+	      `(inst ,op r y x)
+	      `(inst ,op r x y))))
+     ,@(unless arg-swap
+	 `((define-vop (,(symbolicate 'fast- translate '-c/unsigned=>unsigned)
+			fast-unsigned-binop-c)
+	     (:translate ,translate)
+	     (:generator ,untagged-penalty
+	       (inst ,op r x y)))))))
 
 ); eval-when
 
 (define-binop + 4 add)
 (define-binop - 4 sub)
 (define-binop logand 2 and)
+(define-binop logandc1 2 andn t)
 (define-binop logandc2 2 andn)
 (define-binop logior 2 or)
-(define-binop logorc2 2 orn)
+(define-binop logorc1 2 orn t t)
+(define-binop logorc2 2 orn nil t)
 (define-binop logxor 2 xor)
-(define-binop logeqv 2 xnor)
-
-;;; Special logand cases: (logand signed unsigned) => unsigned
-
-(define-vop (fast-logand/signed-unsigned=>unsigned
-	     fast-logand/unsigned=>unsigned)
-    (:args (x :scs (signed-reg))
-	   (y :target r :scs (unsigned-reg)))
-  (:arg-types signed-num unsigned-num))
-
-(define-vop (fast-logand/unsigned-signed=>unsigned
-	     fast-logand/unsigned=>unsigned)
-    (:args (x :target r :scs (unsigned-reg))
-	   (y :scs (signed-reg)))
-  (:arg-types unsigned-num signed-num))
-    
+(define-binop logeqv 2 xnor nil t)
+
 ;;; Special case fixnum + and - that trap on overflow.  Useful when we
 ;;; don't know that the output type is a fixnum.
 
-;;; I (Raymond Toy) took these out. They don't seem to be used anywhere at all.
+;;; I (Raymond Toy) took these out. They don't seem to be used
+;;; anywhere at all.
 #+nil
 (progn
 (define-vop (+/fixnum fast-+/fixnum=>fixnum)
@@ -380,7 +387,7 @@
 (define-vop (fast-ash/signed=>signed)
   (:note "inline ASH")
   (:args (number :scs (signed-reg) :to :save)
-	 (amount :scs (signed-reg immediate) :to :save))
+	 (amount :scs (signed-reg) :to :save))
   (:arg-types signed-num signed-num)
   (:results (result :scs (signed-reg)))
   (:result-types signed-num)
@@ -388,32 +395,43 @@
   (:policy :fast-safe)
   (:temporary (:sc non-descriptor-reg) ndesc)
   (:generator 5
-    (sc-case amount
-      (signed-reg
-       (let ((done (gen-label)))
-	 (inst cmp amount)
-	 (inst b :ge done)
-	 ;; The result-type assures us that this shift will not
-	 ;; overflow.
-	 (inst sll result number amount)
-	 (inst neg ndesc amount)
-	 (inst cmp ndesc 31)
-	 (if (member :sparc-v9 *backend-subfeatures*)
-	     (progn
-	       (inst cmove :ge ndesc 31)
-	       (inst sra result number ndesc))
-	     (progn
-	       (inst b :le done)
-	       (inst sra result number ndesc)
-	       (inst sra result number 31)))
-	 (emit-label done)))
-      (immediate
-       (bug "IMMEDIATE case in ASH VOP; should have been transformed")))))
+    (let ((done (gen-label)))
+      (inst cmp amount)
+      (inst b :ge done)
+      ;; The result-type assures us that this shift will not
+      ;; overflow.
+      (inst sll result number amount)
+      (inst neg ndesc amount)
+      (inst cmp ndesc 31)
+      (if (member :sparc-v9 *backend-subfeatures*)
+	  (progn
+	    (inst cmove :ge ndesc 31)
+	    (inst sra result number ndesc))
+	  (progn
+	    (inst b :le done)
+	    (inst sra result number ndesc)
+	    (inst sra result number 31)))
+      (emit-label done))))
+
+(define-vop (fast-ash-c/signed=>signed)
+  (:note "inline constant ASH")
+  (:args (number :scs (signed-reg)))
+  (:info count)
+  (:arg-types signed-num (:constant integer))
+  (:results (result :scs (signed-reg)))
+  (:result-types signed-num)
+  (:translate ash)
+  (:policy :fast-safe)
+  (:generator 4
+    (cond
+      ((< count 0) (inst sra result number (min (- count) 31)))
+      ((> count 0) (inst sll result number (min count 31)))
+      (t (bug "identity ASH not transformed away")))))
 
 (define-vop (fast-ash/unsigned=>unsigned)
   (:note "inline ASH")
   (:args (number :scs (unsigned-reg) :to :save)
-	 (amount :scs (signed-reg immediate) :to :save))
+	 (amount :scs (signed-reg) :to :save))
   (:arg-types unsigned-num signed-num)
   (:results (result :scs (unsigned-reg)))
   (:result-types unsigned-num)
@@ -421,27 +439,39 @@
   (:policy :fast-safe)
   (:temporary (:sc non-descriptor-reg) ndesc)
   (:generator 5
-    (sc-case amount
-      (signed-reg
-       (let ((done (gen-label)))
-	 (inst cmp amount)
-	 (inst b :ge done)
-	 ;; The result-type assures us that this shift will not
-	 ;; overflow.
-	 (inst sll result number amount)
-	 (inst neg ndesc amount)
-	 (inst cmp ndesc 32)
-	 (if (member :sparc-v9 *backend-subfeatures*)
-	     (progn
-	       (inst srl result number ndesc)
-	       (inst cmove :ge result zero-tn))
-	     (progn
-	       (inst b :lt done)
-	       (inst srl result number ndesc)
-	       (move result zero-tn)))
-	 (emit-label done)))
-      (immediate
-       (bug "IMMEDIATE case in ASH VOP; should have been transformed")))))
+    (let ((done (gen-label)))
+      (inst cmp amount)
+      (inst b :ge done)
+      ;; The result-type assures us that this shift will not
+      ;; overflow.
+      (inst sll result number amount)
+      (inst neg ndesc amount)
+      (inst cmp ndesc 32)
+      (if (member :sparc-v9 *backend-subfeatures*)
+	  (progn
+	    (inst srl result number ndesc)
+	    (inst cmove :ge result zero-tn))
+	  (progn
+	    (inst b :lt done)
+	    (inst srl result number ndesc)
+	    (move result zero-tn)))
+      (emit-label done))))
+
+(define-vop (fast-ash-c/unsigned=>unsigned)
+  (:note "inline constant ASH")
+  (:args (number :scs (unsigned-reg)))
+  (:info count)
+  (:arg-types unsigned-num (:constant integer))
+  (:results (result :scs (unsigned-reg)))
+  (:result-types unsigned-num)
+  (:translate ash)
+  (:policy :fast-safe)
+  (:generator 4
+    (cond
+      ((< count -31) (move result zero-tn))
+      ((< count 0) (inst srl result number (min (- count) 31)))
+      ((> count 0) (inst sll result number (min count 31)))
+      (t (bug "identity ASH not transformed away")))))
 
 ;; Some special cases where we know we want a left shift.  Just do the
 ;; shift, instead of checking for the sign of the shift.
@@ -465,70 +495,12 @@
 	    (inst sll result number amount))
 	   (immediate
 	    (let ((amount (tn-value amount)))
-	      (assert (>= amount 0))
+	      (aver (>= amount 0))
 	      (inst sll result number amount))))))))
   (frob fast-ash-left/signed=>signed signed-reg signed-num signed-reg 3)
   (frob fast-ash-left/fixnum=>fixnum any-reg tagged-num any-reg 2)
   (frob fast-ash-left/unsigned=>unsigned unsigned-reg unsigned-num unsigned-reg 3))
 
-(defknown ash-right-signed ((signed-byte #.sb!vm:n-word-bits)
-			    (and fixnum unsigned-byte))
-  (signed-byte #.sb!vm:n-word-bits)
-  (movable foldable flushable))
-
-(defknown ash-right-unsigned ((unsigned-byte #.sb!vm:n-word-bits)
-			      (and fixnum unsigned-byte))
-  (unsigned-byte #.sb!vm:n-word-bits)
-  (movable foldable flushable))
-
-;; Some special cases where we want a right shift.  Just do the shift.
-;; (Needs appropriate deftransforms to call these, though.)
-
-(macrolet
-    ((frob (trans name sc-type type shift-inst cost)
-       `(define-vop (,name)
-	 (:note "inline right ASH")
-	 (:translate ,trans)
-	 (:args (number :scs (,sc-type))
-	        (amount :scs (signed-reg unsigned-reg immediate)))
-	 (:arg-types ,type positive-fixnum)
-	 (:results (result :scs (,sc-type)))
-	 (:result-types ,type)
-	 (:policy :fast-safe)
-	 (:generator ,cost
-	    (sc-case amount
-	     ((signed-reg unsigned-reg)
-		(inst ,shift-inst result number amount))
-	     (immediate
-	      (let ((amt (tn-value amount)))
-		(inst ,shift-inst result number amt))))))))
-  (frob ash-right-signed fast-ash-right/signed=>signed
-	signed-reg signed-num sra 3)
-  (frob ash-right-unsigned fast-ash-right/unsigned=>unsigned
-	unsigned-reg unsigned-num srl 3))
-
-(define-vop (fast-ash-right/fixnum=>fixnum)
-    (:note "inline right ASH")
-  (:translate ash-right-signed)
-  (:args (number :scs (any-reg))
-	 (amount :scs (signed-reg unsigned-reg immediate)))
-  (:arg-types tagged-num positive-fixnum)
-  (:results (result :scs (any-reg)))
-  (:result-types tagged-num)
-  (:temporary (:sc non-descriptor-reg :target result) temp)
-  (:policy :fast-safe)
-  (:generator 2
-    ;; Shift the fixnum right by the desired amount.  Then zap out the
-    ;; 2 LSBs to make it a fixnum again.  (Those bits are junk.)
-    (sc-case amount
-      ((signed-reg unsigned-reg)
-       (inst sra temp number amount))
-      (immediate
-       (inst sra temp number (tn-value amount))))
-    (inst andn result temp fixnum-tag-mask)))
-    
-
-
 
 (define-vop (signed-byte-32-len)
   (:translate integer-length)
@@ -668,6 +640,50 @@
     (inst mulx r x y)))
 
 
+;;;; Modular functions:
+(define-modular-fun lognot-mod32 (x) lognot 32)
+(define-vop (lognot-mod32/unsigned=>unsigned)
+  (:translate lognot-mod32)
+  (:args (x :scs (unsigned-reg)))
+  (:arg-types unsigned-num)
+  (:results (res :scs (unsigned-reg)))
+  (:result-types unsigned-num)
+  (:policy :fast-safe)
+  (:generator 1
+    (inst not res x)))
+
+(macrolet
+    ((define-modular-backend (fun &optional constantp)
+       (let ((mfun-name (symbolicate fun '-mod32))
+             (modvop (symbolicate 'fast- fun '-mod32/unsigned=>unsigned))
+             (modcvop (symbolicate 'fast- fun '-mod32-c/unsigned=>unsigned))
+             (vop (symbolicate 'fast- fun '/unsigned=>unsigned))
+             (cvop (symbolicate 'fast- fun '-c/unsigned=>unsigned)))
+         `(progn
+            (define-modular-fun ,mfun-name (x y) ,fun 32)
+            (define-vop (,modvop ,vop)
+              (:translate ,mfun-name))
+	    ,@(when constantp
+		`((define-vop (,modcvop ,cvop)
+		    (:translate ,mfun-name))))))))
+  (define-modular-backend + t)
+  (define-modular-backend - t)
+  (define-modular-backend logxor t)
+  (define-modular-backend logeqv t)
+  (define-modular-backend logandc1)
+  (define-modular-backend logandc2 t)
+  (define-modular-backend logorc1)
+  (define-modular-backend logorc2 t))
+
+(define-source-transform lognand (x y)
+  `(lognot (logand ,x ,y)))
+(define-source-transform lognor (x y)
+  `(lognot (logior ,x ,y)))
+
+(define-vop (fast-ash-left-mod32-c/unsigned=>unsigned
+	     fast-ash-c/unsigned=>unsigned)
+  (:translate ash-left-mod32))
+
 ;;;; Binary conditional VOPs:
 
 (define-vop (fast-conditional)
@@ -781,7 +797,6 @@
 
 
 ;;;; 32-bit logical operations
-
 (define-vop (merge-bits)
   (:translate merge-bits)
   (:args (shift :scs (signed-reg unsigned-reg))
@@ -804,64 +819,38 @@
       (emit-label done)
       (move result res))))
 
+(define-source-transform 32bit-logical-not (x)
+  `(logand (lognot (the (unsigned-byte 32) ,x)) #.(1- (ash 1 32))))
 
-(define-vop (32bit-logical)
-  (:args (x :scs (unsigned-reg zero))
-	 (y :scs (unsigned-reg zero)))
-  (:arg-types unsigned-num unsigned-num)
-  (:results (r :scs (unsigned-reg)))
-  (:result-types unsigned-num)
-  (:policy :fast-safe))
+(deftransform 32bit-logical-and ((x y))
+  '(logand x y))
 
-(define-vop (32bit-logical-not 32bit-logical)
-  (:translate 32bit-logical-not)
-  (:args (x :scs (unsigned-reg zero)))
-  (:arg-types unsigned-num)
-  (:generator 1
-    (inst not r x)))
+(deftransform 32bit-logical-nand ((x y))
+  '(logand (lognand x y) #.(1- (ash 1 32))))
 
-(define-vop (32bit-logical-and 32bit-logical)
-  (:translate 32bit-logical-and)
-  (:generator 1
-    (inst and r x y)))
+(deftransform 32bit-logical-or ((x y))
+  '(logior x y))
 
-(deftransform 32bit-logical-nand ((x y) (* *))
-  '(32bit-logical-not (32bit-logical-and x y)))
+(deftransform 32bit-logical-nor ((x y))
+  '(logand (lognor x y) #.(1- (ash 1 32))))
 
-(define-vop (32bit-logical-or 32bit-logical)
-  (:translate 32bit-logical-or)
-  (:generator 1
-    (inst or r x y)))
+(deftransform 32bit-logical-xor ((x y))
+  '(logxor x y))
 
-(deftransform 32bit-logical-nor ((x y) (* *))
-  '(32bit-logical-not (32bit-logical-or x y)))
+(deftransform 32bit-logical-eqv ((x y))
+  '(logand (logeqv x y) #.(1- (ash 1 32))))
 
-(define-vop (32bit-logical-xor 32bit-logical)
-  (:translate 32bit-logical-xor)
-  (:generator 1
-    (inst xor r x y)))
+(deftransform 32bit-logical-orc1 ((x y))
+  '(logand (logorc1 x y) #.(1- (ash 1 32))))
 
-(define-vop (32bit-logical-eqv 32bit-logical)
-  (:translate 32bit-logical-eqv)
-  (:generator 1
-    (inst xnor r x y)))
+(deftransform 32bit-logical-orc2 ((x y))
+  '(logand (logorc2 x y) #.(1- (ash 1 32))))
 
-(define-vop (32bit-logical-orc2 32bit-logical)
-  (:translate 32bit-logical-orc2)
-  (:generator 1
-    (inst orn r x y)))
-
-(deftransform 32bit-logical-orc1 ((x y) (* *))
-  '(32bit-logical-orc2 y x))
-
-(define-vop (32bit-logical-andc2 32bit-logical)
-  (:translate 32bit-logical-andc2)
-  (:generator 1
-    (inst andn r x y)))
-
-(deftransform 32bit-logical-andc1 ((x y) (* *))
-  '(32bit-logical-andc2 y x))
+(deftransform 32bit-logical-andc1 ((x y))
+  '(logand (logandc1 x y) #.(1- (ash 1 32))))
 
+(deftransform 32bit-logical-andc2 ((x y))
+  '(logand (logandc2 x y) #.(1- (ash 1 32))))
 
 (define-vop (shift-towards-someplace)
   (:policy :fast-safe)
@@ -882,12 +871,8 @@
   (:note "shift-towards-end")
   (:generator 1
     (inst srl r num amount)))
-
-
-
 
 ;;;; Bignum stuff.
-
 (define-vop (bignum-length get-header-data)
   (:translate sb!bignum::%bignum-length)
   (:policy :fast-safe))
@@ -954,7 +939,6 @@
     (inst movr result null-tn digit :lz)
     (inst movr result temp digit :gez)))
 
-
 (define-vop (add-w/carry)
   (:translate sb!bignum::%add-with-carry)
   (:policy :fast-safe)
@@ -1083,15 +1067,8 @@
   (:generator 40
     (emit-multiply x y hi lo)))
 
-(define-vop (bignum-lognot)
-  (:translate sb!bignum::%lognot)
-  (:policy :fast-safe)
-  (:args (x :scs (unsigned-reg)))
-  (:arg-types unsigned-num)
-  (:results (r :scs (unsigned-reg)))
-  (:result-types unsigned-num)
-  (:generator 1
-    (inst not r x)))
+(define-vop (bignum-lognot lognot-mod32/unsigned=>unsigned)
+  (:translate sb!bignum::%lognot))
 
 (define-vop (fixnum-to-digit)
   (:translate sb!bignum::%fixnum-to-digit)
@@ -1192,7 +1169,6 @@
       (signed-reg
        (move res digit)))))
 
-
 (define-vop (digit-ashr)
   (:translate sb!bignum::%ashr)
   (:policy :fast-safe)
@@ -1237,115 +1213,26 @@
 (define-static-fun two-arg-and (x y) :translate logand)
 (define-static-fun two-arg-ior (x y) :translate logior)
 (define-static-fun two-arg-xor (x y) :translate logxor)
+(define-static-fun two-arg-eqv (x y) :translate logeqv)
 
 
-;; Need these so constant folding works with the deftransform.
-
-;; FIXME KLUDGE ew yuk.
-#-sb-xc-host
-(progn
-  (defun ash-right-signed (num shift)
-    (ash-right-signed num shift))
-
-  (defun ash-right-unsigned (num shuft)
-    (ash-right-unsigned num shift)))
-
 (in-package "SB!C")
 
-;;; If both arguments and the result are (UNSIGNED-BYTE 32), try to
-;;; come up with a ``better'' multiplication using multiplier
-;;; recoding. There are two different ways the multiplier can be
-;;; recoded. The more obvious is to shift X by the correct amount for
-;;; each bit set in Y and to sum the results. But if there is a string
-;;; of bits that are all set, you can add X shifted by one more then
-;;; the bit position of the first set bit and subtract X shifted by
-;;; the bit position of the last set bit. We can't use this second
-;;; method when the high order bit is bit 31 because shifting by 32
-;;; doesn't work too well.
 (deftransform * ((x y)
 		 ((unsigned-byte 32) (constant-arg (unsigned-byte 32)))
 		 (unsigned-byte 32))
   "recode as shifts and adds"
-  (let ((y (continuation-value y))
-	(adds 0)
-	(shifts 0)
-	(result nil)
-	(first-one nil))
-    (labels ((tub32 (x) `(truly-the (unsigned-byte 32) ,x))
-	     (add (next-factor)
-	       (setf result
-		     (tub32
-		      (if result
-			  (progn (incf adds) `(+ ,result ,(tub32 next-factor)))
-			  next-factor)))))
-      (declare (inline add))
-      (dotimes (bitpos 32)
-	(if first-one
-	    (when (not (logbitp bitpos y))
-	      (add (if (= (1+ first-one) bitpos)
-		       ;; There is only a single bit in the string.
-		       (progn (incf shifts) `(ash x ,first-one))
-		       ;; There are at least two.
-		       (progn
-			 (incf adds)
-			 (incf shifts 2)
-			 `(- ,(tub32 `(ash x ,bitpos))
-			     ,(tub32 `(ash x ,first-one))))))
-	      (setf first-one nil))
-	    (when (logbitp bitpos y)
-	      (setf first-one bitpos))))
-      (when first-one
-	(cond ((= first-one 31))
-	      ((= first-one 30) (incf shifts) (add '(ash x 30)))
-	      (t
-	       (incf shifts 2)
-	       (incf adds)
-	       (add `(- ,(tub32 '(ash x 31)) ,(tub32 `(ash x ,first-one))))))
-	(incf shifts)
-	(add '(ash x 31))))
-
-    (cond
-      ;; we assume, perhaps foolishly, that good SPARCs don't have an
-      ;; issue with multiplications.  (Remember that there's a
-      ;; different transform for converting x*2^k to a shift).
-      ((member :sparc-64 *backend-subfeatures*) (give-up-ir1-transform))
-      ((or (member :sparc-v9 *backend-subfeatures*)
-	   (member :sparc-v8 *backend-subfeatures*))
-       ;; breakeven point as measured by Raymond Toy
-       (when (> (+ adds shifts) 9)
-	 (give-up-ir1-transform))))
-    
-    (or result 0)))
-
-;; If we can prove that we have a right shift, just do the right shift
-;; instead of calling the inline ASH which has to check for the
-;; direction of the shift at run-time.
-(deftransform ash ((num shift) (integer integer))
-  (let ((num-type (continuation-type num))
-	(shift-type (continuation-type shift)))
-    ;; Can only handle right shifts
-    (unless (csubtypep shift-type (specifier-type '(integer * 0)))
-      (give-up-ir1-transform))
-
-    ;; If we can prove the shift is so large that all bits are shifted
-    ;; out, return the appropriate constant.  If the shift is small
-    ;; enough, call the VOP.  Otherwise, check for the shift size and
-    ;; do the appropriate thing.  (Hmm, could we just leave the IF
-    ;; s-expr and depend on other parts of the compiler to delete the
-    ;; unreachable parts, if any?)
-    (cond ((csubtypep num-type (specifier-type '(signed-byte #.sb!vm:n-word-bits)))
-	   ;; A right shift by 31 is the same as a right shift by
-	   ;; larger amount.  We get just the sign.
-	   (if (csubtypep shift-type (specifier-type '(integer #.(- 1 sb!vm:n-word-bits) 0)))
-	       ;; FIXME: ash-right-{un,}signed package problems
-	       `(sb!vm::ash-right-signed num (- shift))
-	       `(sb!vm::ash-right-signed num (min (- shift) #.(1- sb!vm:n-word-bits)))))
-	  ((csubtypep num-type (specifier-type '(unsigned-byte #.sb!vm:n-word-bits)))
-	   (if (csubtypep shift-type (specifier-type '(integer #.(- 1 sb!vm:n-word-bits) 0)))
-	       `(sb!vm::ash-right-unsigned num (- shift))
-	       `(if (<= shift #.(- sb!vm:n-word-bits))
-		 0
-		 (sb!vm::ash-right-unsigned num (- shift)))))
-	  (t
-	   (give-up-ir1-transform)))))
-
+  (let ((y (lvar-value y)))
+    (multiple-value-bind (result adds shifts)
+	(ub32-strength-reduce-constant-multiply 'x y)
+      (cond
+        ;; we assume, perhaps foolishly, that good SPARCs don't have an
+        ;; issue with multiplications.  (Remember that there's a
+        ;; different transform for converting x*2^k to a shift).
+        ((member :sparc-64 *backend-subfeatures*) (give-up-ir1-transform))
+        ((or (member :sparc-v9 *backend-subfeatures*)
+	     (member :sparc-v8 *backend-subfeatures*))
+	 ;; breakeven point as measured by Raymond Toy
+	 (when (> (+ adds shifts) 9)
+	   (give-up-ir1-transform))))
+      (or result 0))))