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169 lines
3.9 KiB
ArmAsm
169 lines
3.9 KiB
ArmAsm
/* Optimized strcmp implementation for Power7 using 'cmpb' instruction
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Copyright (C) 2014-2020 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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/* The optimization is achieved here through cmpb instruction.
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8byte aligned strings are processed with double word comparision
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and unaligned strings are handled effectively with loop unrolling
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technique */
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#include <sysdep.h>
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#ifndef STRCMP
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# define STRCMP strcmp
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#endif
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/* int [r3] strcmp (const char *s1 [r3], const char *s2 [r4]) */
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.machine power7
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ENTRY_TOCLESS (STRCMP, 4)
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CALL_MCOUNT 2
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or r9, r3, r4
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rldicl. r10, r9, 0, 61 /* are s1 and s2 8 byte aligned..? */
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bne cr0, L(process_unaligned_bytes)
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li r5, 0
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.align 4
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/* process input parameters on double word aligned boundary */
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L(unrollDword):
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ld r8,0(r3)
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ld r10,0(r4)
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cmpb r7,r8,r5
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cmpdi cr7,r7,0
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mr r9,r7
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bne cr7,L(null_found)
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cmpld cr7,r8,r10
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bne cr7,L(different)
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ld r8,8(r3)
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ld r10,8(r4)
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cmpb r7,r8,r5
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cmpdi cr7,r7,0
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mr r9,r7
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bne cr7,L(null_found)
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cmpld cr7,r8,r10
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bne cr7,L(different)
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ld r8,16(r3)
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ld r10,16(r4)
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cmpb r7,r8,r5
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cmpdi cr7,r7,0
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mr r9,r7
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bne cr7,L(null_found)
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cmpld cr7,r8,r10
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bne cr7,L(different)
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ld r8,24(r3)
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ld r10,24(r4)
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cmpb r7,r8,r5
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cmpdi cr7,r7,0
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mr r9,r7
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bne cr7,L(null_found)
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cmpld cr7,r8,r10
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bne cr7,L(different)
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addi r3, r3, 32
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addi r4, r4, 32
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beq cr7, L(unrollDword)
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.align 4
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L(null_found):
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#ifdef __LITTLE_ENDIAN__
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neg r7,r9
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and r9,r9,r7
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li r7,-1
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cntlzd r9,r9
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subfic r9,r9,71
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sld r9,r7,r9
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#else
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cntlzd r9,r9
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li r7,-1
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addi r9,r9,8
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srd r9,r7,r9
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#endif
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or r8,r8,r9
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or r10,r10,r9
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L(different):
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cmpb r9,r8,r10
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#ifdef __LITTLE_ENDIAN__
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addi r7,r9,1
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andc r9,r7,r9
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cntlzd r9,r9
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subfic r9,r9,63
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#else
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not r9,r9
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cntlzd r9,r9
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subfic r9,r9,56
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#endif
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srd r3,r8,r9
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srd r10,r10,r9
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rldicl r10,r10,0,56
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rldicl r3,r3,0,56
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subf r3,r10,r3
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blr
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.align 4
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L(process_unaligned_bytes):
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lbz r9, 0(r3) /* load byte from s1 */
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lbz r10, 0(r4) /* load byte from s2 */
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cmpdi cr7, r9, 0 /* compare *s1 with NULL */
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beq cr7, L(diffOfNULL) /* if *s1 is NULL , return *s1 - *s2 */
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cmplw cr7, r9, r10 /* compare *s1 and *s2 */
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bne cr7, L(ComputeDiff) /* branch to compute difference and return */
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lbz r9, 1(r3) /* load next byte from s1 */
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lbz r10, 1(r4) /* load next byte from s2 */
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cmpdi cr7, r9, 0 /* compare *s1 with NULL */
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beq cr7, L(diffOfNULL) /* if *s1 is NULL , return *s1 - *s2 */
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cmplw cr7, r9, r10 /* compare *s1 and *s2 */
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bne cr7, L(ComputeDiff) /* branch to compute difference and return */
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lbz r9, 2(r3) /* unroll 3rd byte here */
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lbz r10, 2(r4)
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cmpdi cr7, r9, 0
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beq cr7, L(diffOfNULL)
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cmplw cr7, r9, r10
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bne 7, L(ComputeDiff)
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lbz r9, 3(r3) /* unroll 4th byte now */
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lbz r10, 3(r4)
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addi r3, r3, 4 /* increment s1 by unroll factor */
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cmpdi cr7, r9, 0
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cmplw cr6, 9, r10
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beq cr7, L(diffOfNULL)
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addi r4, r4, 4 /* increment s2 by unroll factor */
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beq cr6, L(process_unaligned_bytes) /* unroll byte processing */
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.align 4
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L(ComputeDiff):
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extsw r9, r9
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subf r10, r10, r9 /* compute s1 - s2 */
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extsw r3, r10
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blr /* return */
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.align 4
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L(diffOfNULL):
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li r9, 0
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subf r10, r10, r9 /* compute s1 - s2 */
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extsw r3, r10 /* sign extend result */
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blr /* return */
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END (STRCMP)
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libc_hidden_builtin_def (strcmp)
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