X-Git-Url: http://repo.macrolet.net/gitweb/?a=blobdiff_plain;f=src%2Fcompiler%2Fx86%2Ftype-vops.lisp;h=0284ae4dd6726308b8a9c78d90946bbe1de71176;hb=09d3e0862347c08634268d49dc2f72c2375b9d8c;hp=9d53fe955d2d89efa997a4cfad3f725ccaf1186a;hpb=d95f1e6476aa63695e018a7769a1ae9e002fca36;p=sbcl.git

diff --git a/src/compiler/x86/type-vops.lisp b/src/compiler/x86/type-vops.lisp
index 9d53fe9..0284ae4 100644
--- a/src/compiler/x86/type-vops.lisp
+++ b/src/compiler/x86/type-vops.lisp
@@ -212,8 +212,27 @@
   (:arg-types unsigned-num)
   (:translate fixnump)
   (:generator 5
+    ;; We could encode this with :Z and SHR, analogously to the signed-byte-32
+    ;; case below -- as we do on x86-64 -- but that costs us an extra
+    ;; register. Compromises...
     (inst cmp value #.sb!xc:most-positive-fixnum)))
 
+(define-vop (fixnump/signed-byte-32 type-predicate)
+  (:args (value :scs (signed-reg)))
+  (:info)
+  (:conditional :z)
+  (:arg-types signed-num)
+  (:translate fixnump)
+  (:generator 5
+    ;; Hackers Delight, p. 53: signed
+    ;;    a <= x <= a + 2^n - 1
+    ;; is equivalent to unsigned
+    ;;    ((x-a) >> n) = 0
+    (inst mov eax-tn value)
+    (inst sub eax-tn #.sb!xc:most-negative-fixnum)
+    (inst shr eax-tn #.(integer-length (- sb!xc:most-positive-fixnum
+                                          sb!xc:most-negative-fixnum)))))
+
 ;;; A (SIGNED-BYTE 32) can be represented with either fixnum or a bignum with
 ;;; exactly one digit.