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/* Copyright (C) 2014 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
#include <sysdep.h>
/* Implements the functions
char * [r3] strncpy (char *dst [r3], const char *src [r4], size_t n [r5])
AND
char * [r3] stpncpy (char *dst [r3], const char *src [r4], size_t n [r5])
The algorithm is as follows:
> if src and dest are 8 byte aligned, perform double word copy
else
> copy byte by byte on unaligned addresses.
The aligned comparison are made using cmpb instructions. */
/* The focus on optimization for performance improvements are as follows:
1. data alignment [gain from aligned memory access on read/write]
2. POWER7 gains performance with loop unrolling/unwinding
[gain by reduction of branch penalty].
3. The final pad with null bytes is done by calling an optimized
memset. */
#ifdef USE_AS_STPNCPY
# define FUNC_NAME __stpncpy
#else
# define FUNC_NAME strncpy
#endif
#define FRAMESIZE (FRAME_MIN_SIZE+32)
#ifndef MEMSET
/* For builds with no IFUNC support, local calls should be made to internal
GLIBC symbol (created by libc_hidden_builtin_def). */
# ifdef SHARED
# define MEMSET __GI_memset
# else
# define MEMSET memset
# endif
#endif
.machine power7
EALIGN(FUNC_NAME, 4, 0)
CALL_MCOUNT 3
mflr r0 /* load link register LR to r0 */
or r10, r3, r4 /* to verify source and destination */
rldicl. r8, r10, 0, 61 /* is double word aligned .. ? */
std r19, -8(r1) /* save callers register , r19 */
std r18, -16(r1) /* save callers register , r18 */
std r0, 16(r1) /* store the link register */
stdu r1, -FRAMESIZE(r1) /* create the stack frame */
mr r9, r3 /* save r3 into r9 for use */
mr r18, r3 /* save r3 for retCode of strncpy */
bne 0, L(byte_by_byte)
srdi r11, r5, 3 /* compute count for CTR ; count = n/8 */
cmpldi cr7, r11, 3 /* if count > 4 ; perform unrolling 4 times */
ble 7, L(update1)
ld r10, 0(r4) /* load doubleWord from src */
cmpb r8, r10, r8 /* compare src with NULL ,we read just now */
cmpdi cr7, r8, 0 /* if cmpb returned NULL ; we continue */
bne cr7, L(update3)
std r10, 0(r3) /* copy doubleword at offset=0 */
ld r10, 8(r4) /* load next doubleword from offset=8 */
cmpb r8, r10, r8 /* compare src with NULL , we read just now */
cmpdi cr7, r8, 0 /* if cmpb returned NULL ; we continue */
bne 7,L(HopBy8)
addi r8, r11, -4
mr r7, r3
srdi r8, r8, 2
mr r6, r4
addi r8, r8, 1
li r12, 0
mtctr r8
b L(dwordCopy)
.p2align 4
L(dWordUnroll):
std r8, 16(r9)
ld r8, 24(r4) /* load dword,perform loop unrolling again */
cmpb r10, r8, r10
cmpdi cr7, r10, 0
bne cr7, L(HopBy24)
std r8, 24(r7) /* copy dword at offset=24 */
addi r9, r9, 32
addi r4, r4, 32
bdz L(leftDwords) /* continue with loop on counter */
ld r3, 32(r6)
cmpb r8, r3, r10
cmpdi cr7, r8, 0
bne cr7, L(update2)
std r3, 32(r7)
ld r10, 40(r6)
cmpb r8, r10, r8
cmpdi cr7, r8, 0
bne cr7, L(HopBy40)
mr r6, r4 /* update values */
mr r7, r9
mr r11, r0
mr r5, r19
L(dwordCopy):
std r10, 8(r9) /* copy dword at offset=8 */
addi r19, r5, -32
addi r0, r11, -4
ld r8, 16(r4)
cmpb r10, r8, r12
cmpdi cr7, r10, 0
beq cr7, L(dWordUnroll)
addi r9, r9, 16 /* increment dst by 16 */
addi r4, r4, 16 /* increment src by 16 */
addi r5, r5, -16 /* decrement length 'n' by 16 */
addi r0, r11, -2 /* decrement loop counter */
L(dWordUnrollOFF):
ld r10, 0(r4) /* load first dword */
li r8, 0 /* load mask */
cmpb r8, r10, r8
cmpdi cr7, r8, 0
bne cr7, L(byte_by_byte)
mtctr r0
li r7, 0
b L(CopyDword)
.p2align 4
L(loadDWordandCompare):
ld r10, 0(r4)
cmpb r8, r10, r7
cmpdi cr7, r8, 0
bne cr7, L(byte_by_byte)
L(CopyDword):
addi r9, r9, 8
std r10, -8(r9)
addi r4, r4, 8
addi r5, r5, -8
bdnz L(loadDWordandCompare)
L(byte_by_byte):
cmpldi cr7, r5, 3
ble cr7, L(verifyByte)
srdi r10, r5, 2
mr r19, r9
mtctr r10
b L(firstByteUnroll)
.p2align 4
L(bytes_unroll):
lbz r10, 1(r4) /* load byte from src */
cmpdi cr7, r10, 0 /* compare for NULL */
stb r10, 1(r19) /* store byte to dst */
beq cr7, L(updtDestComputeN2ndByte)
addi r4, r4, 4 /* advance src */
lbz r10, -2(r4) /* perform loop unrolling for byte r/w */
cmpdi cr7, r10, 0
stb r10, 2(r19)
beq cr7, L(updtDestComputeN3rdByte)
lbz r10, -1(r4) /* perform loop unrolling for byte r/w */
addi r19, r19, 4
cmpdi cr7, r10, 0
stb r10, -1(r19)
beq cr7, L(ComputeNByte)
bdz L(update0)
L(firstByteUnroll):
lbz r10, 0(r4) /* perform loop unrolling for byte r/w */
cmpdi cr7, 10, 0
stb r10, 0(r19)
bne cr7, L(bytes_unroll)
addi r19, r19, 1
L(ComputeNByte):
subf r9, r19, r9 /* compute 'n'n bytes to fill */
add r8, r9, r5
L(zeroFill):
cmpdi cr7, r8, 0 /* compare if length is zero */
beq cr7, L(update3return)
mr r3, r19 /* fill buffer with */
li r4, 0 /* zero fill buffer */
mr r5, r8 /* how many bytes to fill buffer with */
bl MEMSET /* call optimized memset */
nop
L(update3return):
#ifdef USE_AS_STPNCPY
addi r3, r19, -1 /* update return value */
#endif
L(hop2return):
#ifndef USE_AS_STPNCPY
mr r3, r18 /* set return value */
#endif
addi r1, r1, FRAMESIZE /* restore stack pointer */
ld r0, 16(r1) /* read the saved link register */
ld r18, -16(r1) /* restore callers save register, r18 */
ld r19, -8(r1) /* restore callers save register, r19 */
mtlr r0 /* branch to link register */
blr /* return */
.p2align 4
L(update0):
mr r9, r19
.p2align 4
L(verifyByte):
rldicl. r8, r5, 0, 62
#ifdef USE_AS_STPNCPY
mr r3, r9
#endif
beq cr0, L(hop2return)
mtctr r8
addi r4, r4, -1
mr r19, r9
b L(oneBYone)
.p2align 4
L(proceed):
bdz L(done)
L(oneBYone):
lbzu r10, 1(r4) /* copy byte */
addi r19, r19, 1
addi r8, r8, -1
cmpdi cr7, r10, 0
stb r10, -1(r19)
bne cr7, L(proceed)
b L(zeroFill)
.p2align 4
L(done):
addi r1, r1, FRAMESIZE /* restore stack pointer */
#ifdef USE_AS_STPNCPY
mr r3, r19 /* set the return value */
#else
mr r3, r18 /* set the return value */
#endif
ld r0, 16(r1) /* read the saved link register */
ld r18, -16(r1) /* restore callers save register, r18 */
ld r19, -8(r1) /* restore callers save register, r19 */
mtlr r0 /* branch to link register */
blr /* return */
L(update1):
mr r0, r11
mr r19, r5
.p2align 4
L(leftDwords):
cmpdi cr7, r0, 0
mr r5, r19
bne cr7, L(dWordUnrollOFF)
b L(byte_by_byte)
.p2align 4
L(updtDestComputeN2ndByte):
addi r19, r19, 2 /* update dst by 2 */
subf r9, r19, r9 /* compute distance covered */
add r8, r9, r5
b L(zeroFill)
.p2align 4
L(updtDestComputeN3rdByte):
addi r19, r19, 3 /* update dst by 3 */
subf r9, r19, r9 /* compute distance covered */
add r8, r9, r5
b L(zeroFill)
.p2align 4
L(HopBy24):
addi r9, r9, 24 /* increment dst by 24 */
addi r4, r4, 24 /* increment src by 24 */
addi r5, r5, -24 /* decrement length 'n' by 24 */
addi r0, r11, -3 /* decrement loop counter */
b L(dWordUnrollOFF)
.p2align 4
L(update2):
mr r5, r19
b L(dWordUnrollOFF)
.p2align 4
L(HopBy40):
addi r9, r7, 40 /* increment dst by 40 */
addi r4, r6, 40 /* increment src by 40 */
addi r5, r5, -40 /* decrement length 'n' by 40 */
addi r0, r11, -5 /* decrement loop counter */
b L(dWordUnrollOFF)
L(update3):
mr r0, r11
b L(dWordUnrollOFF)
L(HopBy8):
addi r9, r3, 8 /* increment dst by 8 */
addi r4, r4, 8 /* increment src by 8 */
addi r5, r5, -8 /* decrement length 'n' by 8 */
addi r0, r11, -1 /* decrement loop counter */
b L(dWordUnrollOFF)
END(FUNC_NAME)
#ifndef USE_AS_STPNCPY
libc_hidden_builtin_def (strncpy)
#endif
|
