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powerpc: Optimized strncmp for POWER8/PPC64

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This patch adds an optimized POWER8 strncmp.  The implementation focus
on speeding up unaligned cases follwing the ideas of power8 strcmp.

The algorithm first check the initial 16 bytes, then align the first
function source and uses unaligned loads on second argument only.
Aditional checks for page boundaries are done for unaligned cases
(where sources alignment are different).
This commit is contained in:
Adhemerval Zanella 2015-01-09 16:04:26 -05:00
parent 72607db038
commit d3b00f468b
7 changed files with 387 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

11
ChangeLog
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@ -1,3 +1,14 @@
2015-01-13 Adhemerval Zanella <azanella@linux.vnet.ibm.com>
* sysdeps/powerpc/powerpc64/multiarch/strncmp-power8.S: New file.
* sysdeps/powerpc/powerpc64/power8/strncmp.S: New file.
* sysdeps/powerpc/powerpc64/multiarch/Makefile [sysdep_routines]: Add
strncmp-power8 object.
* sysdeps/powerpc/powerpc64/multiarch/ifunc-impl-list.c
(__libc_ifunc_impl_list): Add __strncmp_power8 implementation.
* sysdeps/powerpc/powerpc64/multiarch/strncmp.c (strncmp): Likewise.
* NEWS: Update.
2015-01-13 Rajalakshmi Srinivasaraghavan <raji@linux.vnet.ibm.com>
Adhemerval Zanella <azanella@linux.vnet.ibm.com>

4
NEWS
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@ -19,8 +19,8 @@ Version 2.21
17744, 17745, 17746, 17747, 17748, 17775, 17777, 17780, 17781, 17782,
17791, 17793, 17796, 17797, 17803, 17806, 17834
* Optimized strcpy, stpcpy, strncpy, stpncpy, and strcmp implementations for
powerpc64/powerpc64le.
* Optimized strcpy, stpcpy, strncpy, stpncpy, strcmp, and strncmp
implementations for powerpc64/powerpc64le.
Implemented by Adhemerval Zanella (IBM).
* Added support for TSX lock elision of pthread mutexes on powerpc32, powerpc64

5
sysdeps/powerpc/powerpc64/multiarch/Makefile
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@ -7,8 +7,9 @@ sysdep_routines += memcpy-power7 memcpy-a2 memcpy-power6 memcpy-cell \
memrchr-power7 memrchr-ppc64 rawmemchr-power7 \
rawmemchr-ppc64 strlen-power7 strlen-ppc64 strnlen-power7 \
strnlen-ppc64 strcasecmp-power7 strcasecmp_l-power7 \
strncase-power7 strncase_l-power7 strncmp-power7 \
strncmp-power4 strncmp-ppc64 strchr-power7 strchr-ppc64 \
strncase-power7 strncase_l-power7 \
strncmp-power8 strncmp-power7 strncmp-power4 strncmp-ppc64 \
strchr-power7 strchr-ppc64 \
strchrnul-power7 strchrnul-ppc64 wcschr-power7 \
wcschr-power6 wcschr-ppc64 wcsrchr-power7 wcsrchr-power6 \
wcsrchr-ppc64 wcscpy-power7 wcscpy-power6 wcscpy-ppc64 \

2
sysdeps/powerpc/powerpc64/multiarch/ifunc-impl-list.c
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@ -108,6 +108,8 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
/* Support sysdeps/powerpc/powerpc64/multiarch/strncmp.c. */
IFUNC_IMPL (i, name, strncmp,
IFUNC_IMPL_ADD (array, i, strncmp, hwcap2 & PPC_FEATURE2_ARCH_2_07,
__strncmp_power8)
IFUNC_IMPL_ADD (array, i, strncmp, hwcap & PPC_FEATURE_HAS_VSX,
__strncmp_power7)
IFUNC_IMPL_ADD (array, i, strncmp, hwcap & PPC_FEATURE_POWER4,

40
sysdeps/powerpc/powerpc64/multiarch/strncmp-power8.S Normal file
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@ -0,0 +1,40 @@
/* Copyright (C) 2015 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>
#undef EALIGN
#define EALIGN(name,alignt,words) \
.section ".text"; \
ENTRY_2(__strncmp_power8) \
.align ALIGNARG(alignt); \
EALIGN_W_##words; \
BODY_LABEL(__strncmp_power8): \
cfi_startproc; \
LOCALENTRY(__strncmp_power8)
#undef END
#define END(name) \
cfi_endproc; \
TRACEBACK(__strncmp_power8) \
END_2(__strncmp_power8)
#undef libc_hidden_builtin_def
#define libc_hidden_builtin_def(name)
#include <sysdeps/powerpc/powerpc64/power8/strncmp.S>

9
sysdeps/powerpc/powerpc64/multiarch/strncmp.c
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@ -25,13 +25,16 @@
extern __typeof (strncmp) __strncmp_ppc attribute_hidden;
extern __typeof (strncmp) __strncmp_power4 attribute_hidden;
extern __typeof (strncmp) __strncmp_power7 attribute_hidden;
extern __typeof (strncmp) __strncmp_power8 attribute_hidden;
/* Avoid DWARF definition DIE on ifunc symbol so that GDB can handle
ifunc symbol properly. */
libc_ifunc (strncmp,
(hwcap & PPC_FEATURE_HAS_VSX)
? __strncmp_power7 :
(hwcap & PPC_FEATURE_POWER4)
(hwcap2 & PPC_FEATURE2_ARCH_2_07)
? __strncmp_power8 :
(hwcap & PPC_FEATURE_HAS_VSX)
? __strncmp_power7 :
(hwcap & PPC_FEATURE_POWER4)
? __strncmp_power4
: __strncmp_ppc);
#endif

323
sysdeps/powerpc/powerpc64/power8/strncmp.S Normal file
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@ -0,0 +1,323 @@
/* Optimized strncmp implementation for PowerPC64/POWER8.
Copyright (C) 2015 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 function
int [r3] strncmp (const char *s1 [r3], const char *s2 [r4], size_t [r5] n)
The implementation uses unaligned doubleword access to avoid specialized
code paths depending of data alignment. Although recent powerpc64 uses
64K as default, the page cross handling assumes minimum page size of
4k. */
.machine power7
EALIGN (strncmp, 4, 0)
/* Check if size is 0. */
mr. r10,r5
beq cr0,L(ret0)
/* Check if [s1]+16 or [s2]+16 will cross a 4K page boundary using
the code:
(((size_t) s1) % PAGE_SIZE > (PAGE_SIZE - ITER_SIZE))
with PAGE_SIZE being 4096 and ITER_SIZE begin 16. */
rldicl r8,r3,0,52
cmpldi cr7,r8,4096-16
bgt cr7,L(pagecross)
rldicl r9,r4,0,52
cmpldi cr7,r9,4096-16
bgt cr7,L(pagecross)
/* For short string up to 16 bytes, load both s1 and s2 using
unaligned dwords and compare. */
ld r7,0(r3)
ld r9,0(r4)
li r8,0
cmpb r8,r7,r8
cmpb r6,r7,r9
orc. r8,r8,r6
bne cr0,L(different1)
/* If the string compared are equal, but size is less or equal
to 8, return 0. */
cmpldi cr7,r10,8
li r9,0
ble cr7,L(ret1)
addi r5,r10,-8
ld r7,8(r3)
ld r9,8(r4)
cmpb r8,r7,r8
cmpb r6,r7,r9
orc. r8,r8,r6
bne cr0,L(different0)
cmpldi cr7,r5,8
mr r9,r8
ble cr7,L(ret1)
/* Update pointers and size. */
addi r10,r10,-16
addi r3,r3,16
addi r4,r4,16
/* Now it has checked for first 16 bytes, align source1 to doubleword
and adjust source2 address. */
L(align_8b):
rldicl r5,r3,0,61
rldicr r3,r3,0,60
subf r4,r5,r4
add r10,r10,r5
/* At this point, source1 alignment is 0 and source2 alignment is
between 0 and 7. Check is source2 alignment is 0, meaning both
sources have the same alignment. */
andi. r8,r4,0x7
beq cr0,L(loop_eq_align_0)
li r5,0
b L(loop_ne_align_1)
/* If source2 is unaligned to doubleword, the code needs to check
on each interation if the unaligned doubleword access will cross
a 4k page boundary. */
.align 4
L(loop_ne_align_0):
ld r7,0(r3)
ld r9,0(r4)
cmpb r8,r7,r5
cmpb r6,r7,r9
orc. r8,r8,r6
bne cr0,L(different1)
cmpldi cr7,r10,8
ble cr7,L(ret0)
addi r10,r10,-8
addi r3,r3,8
addi r4,r4,8
L(loop_ne_align_1):
rldicl r9,r4,0,52
cmpldi r7,r9,4088
ble cr7,L(loop_ne_align_0)
cmpdi cr7,r10,0
beq cr7,L(ret0)
lbz r9,0(r3)
lbz r8,0(r4)
cmplw cr7,r9,r8
bne cr7,L(byte_ne_4)
cmpdi cr7,r9,0
beq cr7,L(size_reached_0)
li r9,r7
addi r8,r3,1
mtctr r9
addi r4,r4,1
addi r10,r10,-1
addi r3,r3,8
/* The unaligned read of source2 will cross a 4K page boundary,
and the different byte or NULL maybe be in the remaining page
bytes. Since it can not use the unaligned load the algorithm
reads and compares 8 bytes to keep source1 doubleword aligned. */
.align 4
L(loop_ne_align_byte):
cmpdi cr7,r10,0
addi r10,r10,-1
beq cr7,L(ret0)
lbz r9,0(r8)
lbz r7,0(r4)
addi r8,r8,1
addi r4,r4,1
cmplw cr7,r9,r7
cmpdi cr5,r9,0
bne cr7,L(size_reached_2)
beq cr5,L(size_reached_0)
bdnz L(loop_ne_align_byte)
cmpdi cr7,r10,0
bne+ cr7,L(loop_ne_align_0)
.align 4
L(ret0):
li r9,0
L(ret1):
mr r3,r9
blr
/* The code now check if r8 and r10 are different by issuing a
cmpb and shift the result based on its output:
#ifdef __LITTLE_ENDIAN__
leadzero = (__builtin_ffsl (z1) - 1);
leadzero = leadzero > (n-1)*8 ? (n-1)*8 : leadzero;
r1 = (r1 >> leadzero) & 0xFFUL;
r2 = (r2 >> leadzero) & 0xFFUL;
#else
leadzero = __builtin_clzl (z1);
leadzero = leadzero > (n-1)*8 ? (n-1)*8 : leadzero;
r1 = (r1 >> (56 - leadzero)) & 0xFFUL;
r2 = (r2 >> (56 - leadzero)) & 0xFFUL;
#endif
return r1 - r2; */
.align 4
L(different0):
mr r10,r5
#ifdef __LITTLE_ENDIAN__
L(different1):
neg r11,r8
sldi r10,r10,3
and r8,r11,r8
addi r10,r10,-8
cntlzd r8,r8
subfic r8,r8,63
extsw r8,r8
cmpld cr7,r8,r10
ble cr7,L(different2)
mr r8,r10
L(different2):
extsw r8,r8
#else
L(different1):
addi r10,r10,-1
cntlzd r8,r8
sldi r10,r10,3
cmpld cr7,r8,r10
blt cr7,L(different2)
mr r8,r10
L(different2):
subfic r8,r8,56
#endif
srd r7,r7,r8
srd r9,r9,r8
rldicl r3,r7,0,56
rldicl r9,r9,0,56
subf r9,r9,3
extsw r9,r9
mr r3,r9
blr
/* If unaligned 16 bytes reads across a 4K page boundary, it uses
a simple byte a byte comparison until the page alignment for s1
is reached. */
.align 4
L(pagecross):
lbz r7,0(r3)
lbz r9,0(r4)
subfic r8,r8,4095
cmplw cr7,r9,r7
bne cr7,L(byte_ne_3)
cmpdi cr7,r9,0
beq cr7,L(byte_ne_0)
addi r10,r10,-1
subf r7,r8,r10
subf r9,r7,r10
addi r9,r9,1
mtctr r9
b L(pagecross_loop1)
.align 4
L(pagecross_loop0):
beq cr7,L(ret0)
lbz r9,0(r3)
lbz r8,0(r4)
addi r10,r10,-1
cmplw cr7,r9,r8
cmpdi cr5,r9,0
bne r7,L(byte_ne_2)
beq r5,L(byte_ne_0)
L(pagecross_loop1):
cmpdi cr7,r10,0
addi r3,r3,1
addi r4,r4,1
bdnz L(pagecross_loop0)
cmpdi cr7,r7,0
li r9,0
bne+ cr7,L(align_8b)
b L(ret1)
/* If both source1 and source2 are doubleword aligned, there is no
need for page boundary cross checks. */
.align 4
L(loop_eq_align_0):
ld r7,0(r3)
ld r9,0(r4)
cmpb r8,r7,r8
cmpb r6,r7,r9
orc. r8,r8,r6
bne cr0,L(different1)
cmpldi cr7,r10,8
ble cr7,L(ret0)
addi r9,r10,-9
li r5,0
srdi r9,r9,3
addi r9,r9,1
mtctr r9
b L(loop_eq_align_2)
.align 4
L(loop_eq_align_1):
bdz L(ret0)
L(loop_eq_align_2):
ldu r7,8(r3)
addi r10,r10,-8
ldu r9,8(r4)
cmpb r8,r7,r5
cmpb r6,r7,r9
orc. r8,r8,r6
beq cr0,L(loop_eq_align_1)
b L(different1)
.align 4
L(byte_ne_0):
li r7,0
L(byte_ne_1):
subf r9,r9,r7
extsw r9,r9
b L(ret1)
.align 4
L(byte_ne_2):
extsw r7,r9
mr r9,r8
b L(byte_ne_1)
L(size_reached_0):
li r10,0
L(size_reached_1):
subf r9,r9,r10
extsw r9,r9
b L(ret1)
L(size_reached_2):
extsw r10,r9
mr r9,r7
b L(size_reached_1)
L(byte_ne_3):
extsw r7,r7
b L(byte_ne_1)
L(byte_ne_4):
extsw r10,r9
mr r9,r8
b L(size_reached_1)
END(strncmp)
libc_hidden_builtin_def(strncmp)