200 lines
4.5 KiB
ArmAsm
200 lines
4.5 KiB
ArmAsm
/* Optimized strcmp implementation for POWER7/PowerPC32.
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Copyright (C) 2010-2022 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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#include <sysdep.h>
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/* See strlen.s for comments on how the end-of-string testing works. */
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/* int [r3] strncmp (const char *s1 [r3],
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const char *s2 [r4],
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size_t size [r5]) */
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EALIGN (strncmp,5,0)
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#define rTMP2 r0
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#define rRTN r3
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#define rSTR1 r3 /* first string arg */
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#define rSTR2 r4 /* second string arg */
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#define rN r5 /* max string length */
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#define rWORD1 r6 /* current word in s1 */
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#define rWORD2 r7 /* current word in s2 */
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#define rWORD3 r10
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#define rWORD4 r11
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#define rFEFE r8 /* constant 0xfefefeff (-0x01010101) */
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#define r7F7F r9 /* constant 0x7f7f7f7f */
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#define rNEG r10 /* ~(word in s1 | 0x7f7f7f7f) */
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#define rBITDIF r11 /* bits that differ in s1 & s2 words */
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#define rTMP r12
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dcbt 0,rSTR1
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nop
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or rTMP,rSTR2,rSTR1
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lis r7F7F,0x7f7f
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dcbt 0,rSTR2
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nop
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clrlwi. rTMP,rTMP,30
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cmplwi cr1,rN,0
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lis rFEFE,-0x101
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bne L(unaligned)
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/* We are word aligned so set up for two loops. first a word
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loop, then fall into the byte loop if any residual. */
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srwi. rTMP,rN,2
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clrlwi rN,rN,30
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addi rFEFE,rFEFE,-0x101
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addi r7F7F,r7F7F,0x7f7f
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cmplwi cr1,rN,0
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beq L(unaligned)
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mtctr rTMP
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lwz rWORD1,0(rSTR1)
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lwz rWORD2,0(rSTR2)
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b L(g1)
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L(g0):
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lwzu rWORD1,4(rSTR1)
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bne cr1,L(different)
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lwzu rWORD2,4(rSTR2)
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L(g1): add rTMP,rFEFE,rWORD1
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nor rNEG,r7F7F,rWORD1
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bdz L(tail)
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and. rTMP,rTMP,rNEG
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cmpw cr1,rWORD1,rWORD2
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beq L(g0)
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/* OK. We've hit the end of the string. We need to be careful that
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we don't compare two strings as different because of gunk beyond
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the end of the strings... */
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#ifdef __LITTLE_ENDIAN__
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L(endstring):
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slwi rTMP, rTMP, 1
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addi rTMP2, rTMP, -1
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andc rTMP2, rTMP2, rTMP
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and rWORD2, rWORD2, rTMP2 /* Mask off gunk. */
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and rWORD1, rWORD1, rTMP2
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rlwinm rTMP2, rWORD2, 8, 0xffffffff /* Byte reverse word. */
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rlwinm rTMP, rWORD1, 8, 0xffffffff
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rldimi rTMP2, rWORD2, 24, 32
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rldimi rTMP, rWORD1, 24, 32
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rlwimi rTMP2, rWORD2, 24, 16, 23
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rlwimi rTMP, rWORD1, 24, 16, 23
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xor. rBITDIF, rTMP, rTMP2
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sub rRTN, rTMP, rTMP2
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bgelr
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ori rRTN, rTMP2, 1
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blr
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L(different):
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lwz rWORD1, -4(rSTR1)
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rlwinm rTMP2, rWORD2, 8, 0xffffffff /* Byte reverse word. */
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rlwinm rTMP, rWORD1, 8, 0xffffffff
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rldimi rTMP2, rWORD2, 24, 32
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rldimi rTMP, rWORD1, 24, 32
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rlwimi rTMP2, rWORD2, 24, 16, 23
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rlwimi rTMP, rWORD1, 24, 16, 23
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xor. rBITDIF, rTMP, rTMP2
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sub rRTN, rTMP, rTMP2
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bgelr
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ori rRTN, rTMP2, 1
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blr
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#else
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L(endstring):
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and rTMP,r7F7F,rWORD1
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beq cr1,L(equal)
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add rTMP,rTMP,r7F7F
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xor. rBITDIF,rWORD1,rWORD2
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andc rNEG,rNEG,rTMP
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blt L(highbit)
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cntlzw rBITDIF,rBITDIF
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cntlzw rNEG,rNEG
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addi rNEG,rNEG,7
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cmpw cr1,rNEG,rBITDIF
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sub rRTN,rWORD1,rWORD2
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bgelr cr1
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L(equal):
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li rRTN,0
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blr
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L(different):
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lwz rWORD1,-4(rSTR1)
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xor. rBITDIF,rWORD1,rWORD2
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sub rRTN,rWORD1,rWORD2
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bgelr
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L(highbit):
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ori rRTN, rWORD2, 1
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blr
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#endif
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/* Oh well. In this case, we just do a byte-by-byte comparison. */
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.align 4
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L(tail):
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and. rTMP,rTMP,rNEG
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cmpw cr1,rWORD1,rWORD2
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bne L(endstring)
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addi rSTR1,rSTR1,4
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bne cr1,L(different)
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addi rSTR2,rSTR2,4
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cmplwi cr1,rN,0
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L(unaligned):
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mtctr rN
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ble cr1,L(ux)
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L(uz):
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lbz rWORD1,0(rSTR1)
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lbz rWORD2,0(rSTR2)
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.align 4
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L(u1):
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cmpwi cr1,rWORD1,0
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bdz L(u4)
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cmpw rWORD1,rWORD2
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beq cr1,L(u4)
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bne L(u4)
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lbzu rWORD3,1(rSTR1)
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lbzu rWORD4,1(rSTR2)
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cmpwi cr1,rWORD3,0
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bdz L(u3)
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cmpw rWORD3,rWORD4
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beq cr1,L(u3)
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bne L(u3)
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lbzu rWORD1,1(rSTR1)
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lbzu rWORD2,1(rSTR2)
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cmpwi cr1,rWORD1,0
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bdz L(u4)
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cmpw rWORD1,rWORD2
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beq cr1,L(u4)
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bne L(u4)
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lbzu rWORD3,1(rSTR1)
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lbzu rWORD4,1(rSTR2)
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cmpwi cr1,rWORD3,0
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bdz L(u3)
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cmpw rWORD3,rWORD4
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beq cr1,L(u3)
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bne L(u3)
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lbzu rWORD1,1(rSTR1)
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lbzu rWORD2,1(rSTR2)
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b L(u1)
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L(u3): sub rRTN,rWORD3,rWORD4
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blr
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L(u4): sub rRTN,rWORD1,rWORD2
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blr
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L(ux):
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li rRTN,0
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blr
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END (strncmp)
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libc_hidden_builtin_def (strncmp)
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