199 lines
5.1 KiB
ArmAsm
199 lines
5.1 KiB
ArmAsm
/* Optimized memchr implementation for PowerPC64/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] memchr (char *s [r3], int byte [r4], int size [r5]) */
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#ifndef MEMCHR
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# define MEMCHR __memchr
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#endif
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.machine power7
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ENTRY_TOCLESS (MEMCHR)
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CALL_MCOUNT 3
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dcbt 0,r3
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clrrdi r8,r3,3
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insrdi r4,r4,8,48
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/* Calculate the last acceptable address and check for possible
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addition overflow by using satured math:
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r7 = r3 + r5
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r7 |= -(r7 < x) */
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add r7,r3,r5
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subfc r6,r3,r7
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subfe r9,r9,r9
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extsw r6,r9
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or r7,r7,r6
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insrdi r4,r4,16,32
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cmpldi r5,32
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li r9, -1
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rlwinm r6,r3,3,26,28 /* Calculate padding. */
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insrdi r4,r4,32,0
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addi r7,r7,-1
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#ifdef __LITTLE_ENDIAN__
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sld r9,r9,r6
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#else
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srd r9,r9,r6
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#endif
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ble L(small_range)
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ld r12,0(r8) /* Load doubleword from memory. */
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cmpb r3,r12,r4 /* Check for BYTEs in DWORD1. */
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and r3,r3,r9
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clrldi r5,r7,61 /* Byte count - 1 in last dword. */
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clrrdi r7,r7,3 /* Address of last doubleword. */
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cmpldi cr7,r3,0 /* Does r3 indicate we got a hit? */
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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 quadword boundary? If so, skip to
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the main loop. Otherwise, go through the alignment code. */
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bt 28,L(loop_setup)
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/* Handle DWORD2 of pair. */
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ldu r12,8(r8)
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cmpb r3,r12,r4
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cmpldi cr7,r3,0
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bne cr7,L(done)
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L(loop_setup):
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/* The last dword we want to read in the loop below is the one
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containing the last byte of the string, ie. the dword at
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(s + size - 1) & ~7, or r7. The first dword read is at
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r8 + 8, we read 2 * cnt dwords, so the last dword read will
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be at r8 + 8 + 16 * cnt - 8. Solving for cnt gives
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cnt = (r7 - r8) / 16 */
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sub r6,r7,r8
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srdi r6,r6,4 /* Number of loop iterations. */
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mtctr r6 /* Setup the counter. */
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/* Main loop to look for BYTE in the string. Since
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it's a small loop (8 instructions), align it to 32-bytes. */
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.align 5
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L(loop):
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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 byte-checking process for bigger strings. */
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ld r12,8(r8)
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ldu r11,16(r8)
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cmpb r3,r12,r4
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cmpb r9,r11,r4
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or r6,r9,r3 /* Merge everything in one doubleword. */
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cmpldi cr7,r6,0
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bne cr7,L(found)
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bdnz L(loop)
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/* We may have one more dword to read. */
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cmpld r8,r7
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beqlr
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ldu r12,8(r8)
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cmpb r3,r12,r4
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cmpldi cr6,r3,0
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bne cr6,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 doublewords contains BYTE. Check
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the first doubleword and decrement the address in case the first
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doubleword really contains BYTE. */
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cmpldi cr6,r3,0
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addi r8,r8,-8
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bne cr6,L(done)
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/* BYTE must be in the second doubleword. 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,r8,8
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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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doubleword 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 range. */
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L(done):
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#ifdef __LITTLE_ENDIAN__
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addi r0,r3,-1
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andc r0,r0,r3
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popcntd r0,r0 /* Count trailing zeros. */
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#else
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cntlzd r0,r3 /* Count leading zeros before the match. */
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#endif
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cmpld r8,r7 /* Are we on the last dword? */
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srdi r0,r0,3 /* Convert leading/trailing zeros to bytes. */
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add r3,r8,r0
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cmpld cr7,r0,r5 /* If on the last dword, check byte offset. */
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bnelr
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blelr 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 <= 32. */
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.align 4
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L(small_range):
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cmpldi r5,0
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beq L(null)
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ld r12,0(r8) /* Load word from memory. */
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cmpb r3,r12,r4 /* Check for BYTE in DWORD1. */
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and r3,r3,r9
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cmpldi cr7,r3,0
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clrldi r5,r7,61 /* Byte count - 1 in last dword. */
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clrrdi r7,r7,3 /* Address of last doubleword. */
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cmpld r8,r7 /* Are we done already? */
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bne cr7,L(done)
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beqlr
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ldu r12,8(r8)
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cmpb r3,r12,r4
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cmpldi cr6,r3,0
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cmpld r8,r7
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bne cr6,L(done) /* Found something. */
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beqlr /* Hit end of string (length). */
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ldu r12,8(r8)
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cmpb r3,r12,r4
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cmpldi cr6,r3,0
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cmpld r8,r7
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bne cr6,L(done)
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beqlr
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ldu r12,8(r8)
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cmpb r3,r12,r4
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cmpldi cr6,r3,0
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cmpld r8,r7
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bne cr6,L(done)
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beqlr
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ldu r12,8(r8)
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cmpb r3,r12,r4
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cmpldi cr6,r3,0
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bne cr6,L(done)
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blr
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END (MEMCHR)
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weak_alias (__memchr, memchr)
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libc_hidden_builtin_def (memchr)
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