remquo asm: return quotient mod 8, as intended by the spec

this is a lot more efficient and also what is generally wanted.
perhaps the bit shuffling could be more efficient...

diff --git a/src/math/i386/remquo.s b/src/math/i386/remquo.s
index 86ae2dc..37a2445 100644 (file)
--- a/src/math/i386/remquo.s
+++ b/src/math/i386/remquo.s
@@ -2,40 +2,49 @@
 .type remquof,@function
 remquof:
        mov 12(%esp),%ecx
-       fldl 4(%esp)
        fldl 8(%esp)
+       fldl 4(%esp)
+       mov 11(%esp),%dh
+       xor 7(%esp),%dh
        jmp 1f
 
 .global remquol
 .type remquol,@function
 remquol:
        mov 28(%esp),%ecx
-       fldl 4(%esp)
        fldl 16(%esp)
+       fldl 4(%esp)
+       mov 25(%esp),%dh
+       xor 13(%esp),%dh
        jmp 1f
 
 .global remquo
 .type remquo,@function
 remquo:
        mov 20(%esp),%ecx
-       fldl 4(%esp)
        fldl 12(%esp)
-1:     fld %st(1)
+       fldl 4(%esp)
+       mov 19(%esp),%dh
+       xor 11(%esp),%dh
 1:      fprem1
        fnstsw %ax
        sahf
        jp 1b
-       fsubr %st(0),%st(2)
-       fxch %st(2)
-       fdivp
-       mov $0x4f000000,%eax
-       mov %eax,4(%esp)
-       flds 4(%esp)
-       fxch %st(1)
-1:     fprem
-       fnstsw %ax
-       sahf
-       jp 1b
-       fistpl (%ecx)
-       fstp %st(0)
+       fstp %st(1)
+       mov %ah,%dl
+       shr %dl
+       and $1,%dl
+       mov %ah,%al
+       shr $5,%al
+       and $2,%al
+       or %al,%dl
+       mov %ah,%al
+       shl $2,%al
+       and $4,%al
+       or %al,%dl
+       test %dh,%dh
+       jns 1f
+       neg %dl
+1:     movsbl %dl,%edx
+       mov %edx,(%ecx)
        ret