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96d6fd6c40
This patch adds an optimized POWER8 strcpy using unaligned accesses. For strings up to 16 bytes the implementation first calculate the string size, like strlen, and issues a memcpy. For larger strings, source is first aligned to 16 bytes and then tested over a loop that reads 16 bytes am combine the cmpb results for speedup. Special case is added for page cross reads. It shows 30%-60% improvement over the optimized POWER7 one that uses only aligned accesses.
263 lines
6.6 KiB
ArmAsm
263 lines
6.6 KiB
ArmAsm
/* Optimized strcpy/stpcpy implementation for PowerPC64/POWER8.
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Copyright (C) 2015 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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<http://www.gnu.org/licenses/>. */
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#include <sysdep.h>
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#ifdef USE_AS_STPCPY
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# define FUNC_NAME __stpcpy
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#else
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# define FUNC_NAME strcpy
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#endif
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/* Implements the function
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char * [r3] strcpy (char *dest [r3], const char *src [r4])
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or
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char * [r3] stpcpy (char *dest [r3], const char *src [r4])
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if USE_AS_STPCPY is defined.
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The implementation uses unaligned doubleword access to avoid specialized
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code paths depending of data alignment. Although recent powerpc64 uses
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64K as default, the page cross handling assumes minimum page size of
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4k. */
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.machine power7
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EALIGN (FUNC_NAME, 4, 0)
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li r0,0 /* Doubleword with null chars to use
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with cmpb. */
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/* Check if the [src]+15 will cross a 4K page by checking if the bit
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indicating the page size changes. Basically:
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uint64_t srcin = (uint64_t)src;
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uint64_t ob = srcin & 4096UL;
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uint64_t nb = (srcin+15UL) & 4096UL;
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if (ob ^ nb)
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goto pagecross; */
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addi r9,r4,15
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xor r9,r9,r4
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rlwinm. r9,r9,0,19,19
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bne L(pagecross)
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/* For short string (less than 16 bytes), just calculate its size as
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strlen and issues a memcpy if null is found. */
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mr r7,r4
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ld r12,0(r7) /* Load doubleword from memory. */
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cmpb r10,r12,r0 /* Check for null bytes in DWORD1. */
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cmpdi cr7,r10,0 /* If r10 == 0, no null's have been found. */
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bne cr7,L(done)
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ldu r8,8(r7)
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cmpb r10,r8,r0
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cmpdi cr7,r10,0
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bne cr7,L(done)
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b L(loop_before)
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.align 4
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L(pagecross):
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clrrdi r7,r4,3 /* Align the address to doubleword boundary. */
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rlwinm r6,r4,3,26,28 /* Calculate padding. */
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li r5,-1 /* MASK = 0xffffffffffffffff. */
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ld r12,0(r7) /* Load doubleword from memory. */
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#ifdef __LITTLE_ENDIAN__
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sld r5,r5,r6
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#else
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srd r5,r5,r6 /* MASK = MASK >> padding. */
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#endif
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orc r9,r12,r5 /* Mask bits that are not part of the string. */
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cmpb r10,r9,r0 /* Check for null bytes in DWORD1. */
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cmpdi cr7,r10,0 /* If r10 == 0, no null's have been found. */
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bne cr7,L(done)
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ldu r6,8(r7)
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cmpb r10,r6,r0
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cmpdi cr7,r10,0
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bne cr7,L(done)
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ld r12,0(r7)
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cmpb r10,r12,r0
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cmpdi cr7,r10,0
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bne cr7,L(done)
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ldu r6,8(r7)
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cmpb r10,r6,r0
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cmpdi cr7,r10,0
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bne cr7,L(done)
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/* We checked for 24 - x bytes, with x being the source alignment
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(0 <= x <= 16), and no zero has been found. Start the loop
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copy with doubleword aligned address. */
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mr r7,r4
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ld r12, 0(r7)
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ldu r8, 8(r7)
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L(loop_before):
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/* Save the two doublewords readed from source and align the source
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to 16 bytes for the loop. */
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mr r11,r3
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std r12,0(r11)
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std r8,8(r11)
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addi r11,r11,16
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rldicl r9,r4,0,60
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subf r7,r9,r7
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subf r11,r9,r11
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b L(loop_start)
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.align 5
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L(loop):
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std r12, 0(r11)
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std r6, 8(r11)
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addi r11,r11,16
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L(loop_start):
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/* Load two doublewords, compare and merge in a
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single register for speed. This is an attempt
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to speed up the null-checking process for bigger strings. */
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ld r12, 8(r7)
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ldu r6, 16(r7)
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cmpb r10,r12,r0
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cmpb r9,r6,r0
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or r8,r9,r10 /* Merge everything in one doubleword. */
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cmpdi cr7,r8,0
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beq cr7,L(loop)
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/* OK, one (or both) of the doublewords contains a null byte. Check
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the first doubleword and decrement the address in case the first
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doubleword really contains a null byte. */
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addi r4,r7,-8
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cmpdi cr6,r10,0
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addi r7,r7,-8
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bne cr6,L(done2)
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/* The null byte must be in the second doubleword. Adjust the address
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again and move the result of cmpb to r10 so we can calculate the
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length. */
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mr r10,r9
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addi r7,r7,8
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b L(done2)
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/* r10 has the output of the cmpb instruction, that is, it contains
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0xff in the same position as the null byte in the original
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doubleword from the string. Use that to calculate the length. */
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L(done):
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mr r11,r3
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L(done2):
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#ifdef __LITTLE_ENDIAN__
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addi r9, r10, -1 /* Form a mask from trailing zeros. */
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andc r9, r9, r10
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popcntd r6, r9 /* Count the bits in the mask. */
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#else
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cntlzd r6,r10 /* Count leading zeros before the match. */
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#endif
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subf r5,r4,r7
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srdi r6,r6,3 /* Convert leading/trailing zeros to bytes. */
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add r8,r5,r6 /* Compute final length. */
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#ifdef USE_AS_STPCPY
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/* stpcpy returns the dest address plus the size not counting the
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final '\0'. */
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add r3,r11,r8
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#endif
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addi r8,r8,1 /* Final '/0'. */
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cmpldi cr6,r8,8
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mtocrf 0x01,r8
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ble cr6,L(copy_LE_8)
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cmpldi cr1,r8,16
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blt cr1,8f
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/* Handle copies of 0~31 bytes. */
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.align 4
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L(copy_LT_32):
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/* At least 6 bytes to go. */
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blt cr1,8f
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/* Copy 16 bytes. */
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ld r6,0(r4)
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ld r8,8(r4)
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addi r4,r4,16
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std r6,0(r11)
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std r8,8(r11)
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addi r11,r11,16
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8: /* Copy 8 bytes. */
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bf 28,L(tail4)
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ld r6,0(r4)
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addi r4,r4,8
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std r6,0(r11)
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addi r11,r11,8
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.align 4
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/* Copies 4~7 bytes. */
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L(tail4):
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bf 29,L(tail2)
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lwz r6,0(r4)
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stw r6,0(r11)
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bf 30,L(tail5)
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lhz r7,4(r4)
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sth r7,4(r11)
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bflr 31
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lbz r8,6(r4)
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stb r8,6(r11)
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blr
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.align 4
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/* Copies 2~3 bytes. */
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L(tail2):
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bf 30,1f
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lhz r6,0(r4)
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sth r6,0(r11)
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bflr 31
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lbz r7,2(r4)
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stb r7,2(r11)
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blr
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.align 4
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L(tail5):
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bf 31,1f
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lbz r6,4(r4)
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stb r6,4(r11)
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blr
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.align 4
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1:
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bflr 31
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lbz r6,0(r4)
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stb r6,0(r11)
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blr
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/* Handles copies of 0~8 bytes. */
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.align 4
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L(copy_LE_8):
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bne cr6,L(tail4)
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ld r6,0(r4)
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std r6,0(r11)
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blr
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END (FUNC_NAME)
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#ifndef USE_AS_STPCPY
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libc_hidden_builtin_def (strcpy)
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#endif
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