freebsd-dev/lib/libc/amd64/string/bcmp.S
Alan Cox fb41e04787 Eliminate a conditional branch and as a side-effect eliminate a branch to
a return instruction.  (The latter is discouraged by the Opteron
optimization manual because it disables branch prediction for the return
instruction.)

Reviewed by: bde
2005-04-10 18:12:07 +00:00

25 lines
373 B
ArmAsm

#include <machine/asm.h>
__FBSDID("$FreeBSD$");
#if 0
RCSID("$NetBSD: bcmp.S,v 1.1 2001/06/19 00:25:04 fvdl Exp $")
#endif
ENTRY(bcmp)
cld /* set compare direction forward */
movq %rdx,%rcx /* compare by words */
shrq $3,%rcx
repe
cmpsq
jne L1
movq %rdx,%rcx /* compare remainder by bytes */
andq $7,%rcx
repe
cmpsb
L1:
setne %al
movsbl %al,%eax
ret