[Sbcl-commits] CVS: sbcl/src/compiler/x86 arith.lisp,1.37,1.38

[Juho S. <js...@us...>]

Update of /cvsroot/sbcl/sbcl/src/compiler/x86
In directory sc8-pr-cvs1.sourceforge.net:/tmp/cvs-serv20054/src/compiler/x86

Modified Files:
	arith.lisp 
Log Message:
0.9.6.24:
	Faster bignum subtraction and division.
        
        (Patch from sbcl-devel "A microoptimisation of bignum subtraction
        on x86/x86-64" by Lutz Euler on 2005-10-16)


Index: arith.lisp
===================================================================
RCS file: /cvsroot/sbcl/sbcl/src/compiler/x86/arith.lisp,v
retrieving revision 1.37
retrieving revision 1.38
diff -u -d -r1.37 -r1.38
--- arith.lisp	14 Jul 2005 19:13:47 -0000	1.37
+++ arith.lisp	6 Nov 2005 04:00:39 -0000	1.38
@@ -1421,7 +1421,7 @@
 
 
 ;;; For add and sub with carry the sc of carry argument is any-reg so
-;;; the it may be passed as a fixnum or word and thus may be 0, 1, or
+;;; that it may be passed as a fixnum or word and thus may be 0, 1, or
 ;;; 4. This is easy to deal with and may save a fixnum-word
 ;;; conversion.
 (define-vop (add-w/carry)
@@ -1443,8 +1443,8 @@
     (inst mov carry 0)
     (inst adc carry carry)))
 
-;;; Note: the borrow is the oppostite of the x86 convention - 1 for no
-;;; borrow and 0 for a borrow.
+;;; Note: the borrow is 1 for no borrow and 0 for a borrow, the opposite
+;;; of the x86 convention.
 (define-vop (sub-w/borrow)
   (:translate sb!bignum:%subtract-with-borrow)
   (:policy :fast-safe)
@@ -1459,9 +1459,8 @@
     (inst cmp c 1) ; Set the carry flag to 1 if c=0 else to 0
     (move result a)
     (inst sbb result b)
-    (inst mov borrow 0)
-    (inst adc borrow borrow)
-    (inst xor borrow 1)))
+    (inst mov borrow 1)
+    (inst sbb borrow 0)))
 
 
 (define-vop (bignum-mult-and-add-3-arg)