151 lines
3.8 KiB
ArmAsm
151 lines
3.8 KiB
ArmAsm
/* Optimized strcmp implementation for PowerPC.
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Copyright (C) 1997-2022 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] strcmp (const char *s1 [r3], const char *s2 [r4]) */
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EALIGN (strcmp, 4, 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 rWORD1 r5 /* current word in s1 */
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#define rWORD2 r6 /* current word in s2 */
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#define rFEFE r7 /* constant 0xfefefeff (-0x01010101) */
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#define r7F7F r8 /* constant 0x7f7f7f7f */
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#define rNEG r9 /* ~(word in s1 | 0x7f7f7f7f) */
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#define rBITDIF r10 /* bits that differ in s1 & s2 words */
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#define rTMP r11
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or rTMP, rSTR2, rSTR1
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clrlwi. rTMP, rTMP, 30
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lis rFEFE, -0x101
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bne L(unaligned)
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lwz rWORD1, 0(rSTR1)
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lwz rWORD2, 0(rSTR2)
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lis r7F7F, 0x7f7f
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addi rFEFE, rFEFE, -0x101
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addi r7F7F, r7F7F, 0x7f7f
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b L(g1)
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L(g0): 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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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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addi rTMP2, rTMP, -1
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andc rTMP2, rTMP2, rTMP
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rlwimi rTMP2, rTMP2, 1, 0, 30
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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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rlwimi rTMP2, rWORD2, 24, 0, 7
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rlwimi rTMP, rWORD1, 24, 0, 7
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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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rlwimi rTMP2, rWORD2, 24, 0, 7
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rlwimi rTMP, rWORD1, 24, 0, 7
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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(unaligned):
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lbz rWORD1, 0(rSTR1)
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lbz rWORD2, 0(rSTR2)
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b L(u1)
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L(u0): lbzu rWORD1, 1(rSTR1)
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bne- L(u4)
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lbzu rWORD2, 1(rSTR2)
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L(u1): cmpwi cr1, rWORD1, 0
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beq- cr1, L(u3)
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cmpw rWORD1, rWORD2
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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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cmpw rWORD1, rWORD2
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bne+ cr1, L(u0)
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L(u3): sub rRTN, rWORD1, rWORD2
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blr
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L(u4): lbz rWORD1, -1(rSTR1)
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sub rRTN, rWORD1, rWORD2
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blr
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END (strcmp)
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libc_hidden_builtin_def (strcmp)
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