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glibc/sysdeps/i386/i586
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H.J. Lu c5cc45148c i586: Use conditional branches in strcpy.S [BZ #22353] 
i586 strcpy.S used a clever trick with LEA to implement jump table:

/* ECX has the last 2 bits of the address of source - 1.  */
	andl	$3, %ecx

        call    2f
2:      popl    %edx
	/* 0xb is the distance between 2: and 1:.  */
        leal    0xb(%edx,%ecx,8), %ecx
        jmp     *%ecx

        .align 8
1:  /* ECX == 0 */
        orb     (%esi), %al
        jz      L(end)
        stosb
        xorl    %eax, %eax
        incl    %esi
    /* ECX == 1 */
        orb     (%esi), %al
        jz      L(end)
        stosb
        xorl    %eax, %eax
        incl    %esi
    /* ECX == 2 */
        orb     (%esi), %al
        jz      L(end)
        stosb
        xorl    %eax, %eax
        incl    %esi
    /* ECX == 3 */
L(1):   movl    (%esi), %ecx
        leal    4(%esi),%esi

This fails if there are instruction length changes before L(1):.  This
patch replaces it with conditional branches:

	cmpb	$2, %cl
	je	L(Src2)
	ja	L(Src3)
	cmpb	$1, %cl
	je	L(Src1)

L(Src0):

which have similar performance and work with any instruction lengths.

Tested on i586 and i686 with and without --disable-multi-arch.

	[BZ #22353]
	* sysdeps/i386/i586/strcpy.S (STRCPY): Use conditional branches.
	(1): Renamed to ...
	(L(Src0)): This.
	(L(Src1)): New.
	(L(Src2)): Likewise.
	(L(1)): Renamed to ...
	(L(Src3)): This.
2017-10-30 10:02:30 -07:00
..
add_n.S Update copyright dates with scripts/update-copyrights. 2017-01-01 00:14:16 +00:00
addmul_1.S Update copyright dates with scripts/update-copyrights. 2017-01-01 00:14:16 +00:00
bzero.S Replace BZERO_P/PIC with USE_AS_BZERO/SHARED 2015-08-26 08:01:03 -07:00
init-arch.h Update copyright dates with scripts/update-copyrights. 2017-01-01 00:14:16 +00:00
lshift.S Update copyright dates with scripts/update-copyrights. 2017-01-01 00:14:16 +00:00
memcopy.h Update copyright dates with scripts/update-copyrights. 2017-01-01 00:14:16 +00:00
memcpy.S Update copyright dates with scripts/update-copyrights. 2017-01-01 00:14:16 +00:00
mempcpy.S Replace MEMPCPY_P/PIC with USE_AS_MEMPCPY/SHARED 2015-08-26 07:59:32 -07:00
memset.S x86: Remove __memset_zero_constant_len_parameter [BZ #21790] 2017-08-04 10:56:51 -07:00
memusage.h
mul_1.S Update copyright dates with scripts/update-copyrights. 2017-01-01 00:14:16 +00:00
rshift.S Update copyright dates with scripts/update-copyrights. 2017-01-01 00:14:16 +00:00
stpcpy.S
strchr.S Update copyright dates with scripts/update-copyrights. 2017-01-01 00:14:16 +00:00
strcpy.S i586: Use conditional branches in strcpy.S [BZ #22353] 2017-10-30 10:02:30 -07:00
strlen.S Update copyright dates with scripts/update-copyrights. 2017-01-01 00:14:16 +00:00
sub_n.S Update copyright dates with scripts/update-copyrights. 2017-01-01 00:14:16 +00:00
submul_1.S Update copyright dates with scripts/update-copyrights. 2017-01-01 00:14:16 +00:00