platform_bionic/libc/arch-x86/generic/string/memcmp.S
Haibo Huang b9244ff551 Use ifunc to dynamically dispatch libc routines for x86
Test: run bionic unit test in aosp_cf_x86_phone emulator
Change-Id: Ib0c0de37cd38d24bfce2dfbe35b8fd8edff004af
2018-11-13 13:48:23 -08:00

44 lines
885 B
ArmAsm

/* $OpenBSD: memcmp.S,v 1.4 2005/08/07 11:30:38 espie Exp $ */
/*
* Written by J.T. Conklin <jtc@netbsd.org>.
* Public domain.
*/
#include <private/bionic_asm.h>
ENTRY(memcmp_generic)
pushl %edi
pushl %esi
movl 12(%esp),%edi
movl 16(%esp),%esi
cld /* set compare direction forward */
movl 20(%esp),%ecx /* compare by words */
shrl $2,%ecx
repe
cmpsl
jne L5 /* do we match so far? */
movl 20(%esp),%ecx /* compare remainder by bytes */
andl $3,%ecx
repe
cmpsb
jne L6 /* do we match? */
xorl %eax,%eax /* we match, return zero */
popl %esi
popl %edi
ret
L5: movl $4,%ecx /* We know that one of the next */
subl %ecx,%edi /* four pairs of bytes do not */
subl %ecx,%esi /* match. */
repe
cmpsb
L6: movzbl -1(%edi),%eax /* Perform unsigned comparison */
movzbl -1(%esi),%edx
subl %edx,%eax
popl %esi
popl %edi
ret
END(memcmp_generic)