196 lines
4.6 KiB
ArmAsm
196 lines
4.6 KiB
ArmAsm
/* Optimized memrchr implementation for PowerPC32/POWER7 using cmpb insn.
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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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/* int [r3] memrchr (char *s [r3], int byte [r4], int size [r5]) */
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.machine power7
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ENTRY (__memrchr)
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CALL_MCOUNT
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add r7,r3,r5 /* Calculate the last acceptable address. */
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neg r0,r7
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addi r7,r7,-1
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mr r10,r3
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clrrwi r6,r7,7
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li r9,3<<5
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dcbt r9,r6,16 /* Stream hint, decreasing addresses. */
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/* Replicate BYTE to word. */
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insrwi r4,r4,8,16
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insrwi r4,r4,16,0
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li r6,-4
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li r9,-1
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rlwinm r0,r0,3,27,28 /* Calculate padding. */
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clrrwi r8,r7,2
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srw r9,r9,r0
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cmplwi r5,16
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clrrwi r0,r10,2
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ble L(small_range)
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#ifdef __LITTLE_ENDIAN__
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lwzx r12,0,r8
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#else
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lwbrx r12,0,r8 /* Load reversed word from memory. */
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#endif
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cmpb r3,r12,r4 /* Check for BYTE in WORD1. */
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and r3,r3,r9
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cmplwi cr7,r3,0 /* If r3 == 0, no BYTEs have been found. */
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bne cr7,L(done)
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mtcrf 0x01,r8
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/* Are we now aligned to a doubleword boundary? If so, skip to
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the main loop. Otherwise, go through the alignment code. */
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bf 29,L(loop_setup)
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/* Handle WORD2 of pair. */
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#ifdef __LITTLE_ENDIAN__
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lwzx r12,r8,r6
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#else
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lwbrx r12,r8,r6
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#endif
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addi r8,r8,-4
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cmpb r3,r12,r4
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cmplwi cr7,r3,0
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bne cr7,L(done)
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L(loop_setup):
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/* The last word we want to read in the loop below is the one
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containing the first byte of the string, ie. the word at
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s & ~3, or r0. The first word read is at r8 - 4, we
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read 2 * cnt words, so the last word read will be at
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r8 - 4 - 8 * cnt + 4. Solving for cnt gives
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cnt = (r8 - r0) / 8 */
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sub r5,r8,r0
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addi r8,r8,-4
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srwi r9,r5,3 /* Number of loop iterations. */
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mtctr r9 /* Setup the counter. */
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/* Main loop to look for BYTE backwards in the string.
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FIXME: Investigate whether 32 byte align helps with this
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9 instruction loop. */
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.align 5
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L(loop):
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/* Load two words, 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 byte-checking process for bigger strings. */
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#ifdef __LITTLE_ENDIAN__
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lwzx r12,0,r8
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lwzx r11,r8,r6
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#else
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lwbrx r12,0,r8
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lwbrx r11,r8,r6
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#endif
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cmpb r3,r12,r4
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cmpb r9,r11,r4
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or r5,r9,r3 /* Merge everything in one word. */
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cmplwi cr7,r5,0
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bne cr7,L(found)
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addi r8,r8,-8
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bdnz L(loop)
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/* We may have one more word to read. */
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cmplw r8,r0
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bnelr
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#ifdef __LITTLE_ENDIAN__
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lwzx r12,0,r8
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#else
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lwbrx r12,0,r8
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#endif
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cmpb r3,r12,r4
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cmplwi cr7,r3,0
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bne cr7,L(done)
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blr
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.align 4
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L(found):
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/* OK, one (or both) of the words contains BYTE. Check
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the first word. */
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cmplwi cr6,r3,0
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bne cr6,L(done)
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/* BYTE must be in the second word. Adjust the address
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again and move the result of cmpb to r3 so we can calculate the
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pointer. */
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mr r3,r9
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addi r8,r8,-4
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/* r3 has the output of the cmpb instruction, that is, it contains
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0xff in the same position as BYTE in the original
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word from the string. Use that to calculate the pointer.
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We need to make sure BYTE is *before* the end of the
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range. */
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L(done):
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cntlzw r9,r3 /* Count leading zeros before the match. */
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cmplw r8,r0 /* Are we on the last word? */
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srwi r6,r9,3 /* Convert leading zeros to bytes. */
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addi r0,r6,-3
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sub r3,r8,r0
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cmplw cr7,r3,r10
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bnelr
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bgelr cr7
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li r3,0
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blr
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.align 4
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L(null):
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li r3,0
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blr
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/* Deals with size <= 16. */
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.align 4
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L(small_range):
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cmplwi r5,0
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beq L(null)
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#ifdef __LITTLE_ENDIAN__
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lwzx r12,0,r8
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#else
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lwbrx r12,0,r8 /* Load reversed word from memory. */
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#endif
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cmpb r3,r12,r4 /* Check for BYTE in WORD1. */
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and r3,r3,r9
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cmplwi cr7,r3,0
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bne cr7,L(done)
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/* Are we done already? */
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cmplw r8,r0
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addi r8,r8,-4
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beqlr
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.align 5
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L(loop_small):
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#ifdef __LITTLE_ENDIAN__
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lwzx r12,0,r8
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#else
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lwbrx r12,0,r8
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#endif
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cmpb r3,r12,r4
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cmplw r8,r0
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cmplwi cr7,r3,0
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bne cr7,L(done)
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addi r8,r8,-4
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bne L(loop_small)
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blr
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END (__memrchr)
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weak_alias (__memrchr, memrchr)
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libc_hidden_builtin_def (memrchr)
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