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/* Optimized strncmp implementation for PowerPC64/POWER9.
Copyright (C) 2016-2024 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
<https://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 for first 32 bytes and uses
vectorised loops after that. */
#ifndef STRNCMP
# define STRNCMP strncmp
#endif
/* TODO: Change this to actual instructions when minimum binutils is upgraded
to 2.27. Macros are defined below for these newer instructions in order
to maintain compatibility. */
#define VCTZLSBB(r,v) .long (0x10010602 | ((r)<<(32-11)) | ((v)<<(32-21)))
#define VEXTUBRX(t,a,b) .long (0x1000070d \
| ((t)<<(32-11)) \
| ((a)<<(32-16)) \
| ((b)<<(32-21)) )
#define VCMPNEZB(t,a,b) .long (0x10000507 \
| ((t)<<(32-11)) \
| ((a)<<(32-16)) \
| ((b)<<(32-21)) )
/* Get 16 bytes for unaligned case.
reg1: Vector to hold next 16 bytes.
reg2: Address to read from.
reg3: Permute control vector. */
#define GET16BYTES(reg1, reg2, reg3) \
lvx reg1, 0, reg2; \
vperm v8, v2, reg1, reg3; \
vcmpequb. v8, v0, v8; \
beq cr6, 1f; \
vspltisb v9, 0; \
b 2f; \
.align 4; \
1: \
cmplw cr6, r5, r11; \
ble cr6, 2f; \
addi r6, reg2, 16; \
lvx v9, 0, r6; \
2: \
vperm reg1, v9, reg1, reg3;
/* TODO: change this to .machine power9 when minimum binutils
is upgraded to 2.27. */
.machine power7
ENTRY_TOCLESS (STRNCMP, 4)
/* Check if size is 0. */
cmpdi cr0, r5, 0
beq cr0, L(ret0)
li r0, 0
/* Check if [s1]+32 or [s2]+32 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 32. */
rldicl r8, r3, 0, 52
cmpldi cr7, r8, 4096-32
bgt cr7, L(pagecross)
rldicl r9, r4, 0, 52
cmpldi cr7, r9, 4096-32
bgt cr7, L(pagecross)
/* For short strings up to 32 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 strings compared are equal, but size is less or equal
to 8, return 0. */
cmpldi cr7, r5, 8
li r9, 0
ble cr7, L(ret1)
addi r5, r5, -8
ld r7, 8(r3)
ld r9, 8(r4)
cmpb r8, r7, r8
cmpb r6, r7, r9
orc. r8, r8, r6
bne cr0, L(different1)
cmpldi cr7, r5, 8
mr r9, r8
ble cr7, L(ret1)
/* Update pointers and size. */
addi r5, r5, -8
addi r3, r3, 16
addi r4, r4, 16
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)
cmpldi cr7, r5, 8
li r9, 0
ble cr7, L(ret1)
addi r5, r5, -8
ld r7, 8(r3)
ld r9, 8(r4)
cmpb r8, r7, r8
cmpb r6, r7, r9
orc. r8, r8, r6
bne cr0, L(different1)
cmpldi cr7, r5, 8
mr r9, r8
ble cr7, L(ret1)
/* Update pointers and size. */
addi r5, r5, -8
addi r3, r3, 16
addi r4, r4, 16
L(align):
/* Now it has checked for first 32 bytes, align source1 to doubleword
and adjust source2 address. */
vspltisb v0, 0
vspltisb v2, -1
or r6, r4, r3
andi. r6, r6, 0xF
beq cr0, L(aligned)
lvsr v6, 0, r4 /* Compute mask. */
clrldi r6, r4, 60
subfic r11, r6, 16
andi. r6, r3, 0xF
beq cr0, L(s1_align)
/* Both s1 and s2 are unaligned. */
GET16BYTES(v5, r4, v6)
lvsr v10, 0, r3 /* Compute mask. */
clrldi r6, r3, 60
subfic r11, r6, 16
GET16BYTES(v4, r3, v10)
VCMPNEZB(v7, v5, v4)
beq cr6, L(match)
b L(different)
/* Align s1 to qw and adjust s2 address. */
.align 4
L(match):
cmpldi cr7, r5, 16
ble cr7, L(ret0)
subf r5, r11, r5
add r3, r3, r11
add r4, r4, r11
andi. r11, r4, 0xF
beq cr0, L(aligned)
lvsr v6, 0, r4
clrldi r6, r4, 60
subfic r11, r6, 16
/* There are 2 loops depending on the input alignment.
Each loop gets 16 bytes from s1 and s2, checks for null
and compares them. Loops until a mismatch or null occurs. */
L(s1_align):
lvx v4, 0, r3
GET16BYTES(v5, r4, v6)
VCMPNEZB(v7, v5, v4)
bne cr6, L(different)
cmpldi cr7, r5, 16
ble cr7, L(ret0)
addi r5, r5, -16
addi r3, r3, 16
addi r4, r4, 16
lvx v4, 0, r3
GET16BYTES(v5, r4, v6)
VCMPNEZB(v7, v5, v4)
bne cr6, L(different)
cmpldi cr7, r5, 16
ble cr7, L(ret0)
addi r5, r5, -16
addi r3, r3, 16
addi r4, r4, 16
lvx v4, 0, r3
GET16BYTES(v5, r4, v6)
VCMPNEZB(v7, v5, v4)
bne cr6, L(different)
cmpldi cr7, r5, 16
ble cr7, L(ret0)
addi r5, r5, -16
addi r3, r3, 16
addi r4, r4, 16
lvx v4, 0, r3
GET16BYTES(v5, r4, v6)
VCMPNEZB(v7, v5, v4)
bne cr6, L(different)
cmpldi cr7, r5, 16
ble cr7, L(ret0)
addi r5, r5, -16
addi r3, r3, 16
addi r4, r4, 16
b L(s1_align)
.align 4
L(aligned):
lvx v4, 0, r3
lvx v5, 0, r4
VCMPNEZB(v7, v5, v4)
bne cr6, L(different)
cmpldi cr7, r5, 16
ble cr7, L(ret0)
addi r5, r5, -16
addi r3, r3, 16
addi r4, r4, 16
lvx v4, 0, r3
lvx v5, 0, r4
VCMPNEZB(v7, v5, v4)
bne cr6, L(different)
cmpldi cr7, r5, 16
ble cr7, L(ret0)
addi r5, r5, -16
addi r3, r3, 16
addi r4, r4, 16
lvx v4, 0, r3
lvx v5, 0, r4
VCMPNEZB(v7, v5, v4)
bne cr6, L(different)
cmpldi cr7, r5, 16
ble cr7, L(ret0)
addi r5, r5, -16
addi r3, r3, 16
addi r4, r4, 16
lvx v4, 0, r3
lvx v5, 0, r4
VCMPNEZB(v7, v5, v4)
bne cr6, L(different)
cmpldi cr7, r5, 16
ble cr7, L(ret0)
addi r5, r5, -16
addi r3, r3, 16
addi r4, r4, 16
b L(aligned)
/* Calculate and return the difference. */
L(different):
VCTZLSBB(r6, v7)
cmplw cr7, r5, r6
ble cr7, L(ret0)
VEXTUBRX(r5, r6, v4)
VEXTUBRX(r4, r6, v5)
subf r3, r4, r5
extsw r3, r3
blr
.align 4
L(ret0):
li r9, 0
L(ret1):
mr r3, r9
blr
/* The code now checks if r8 and r5 are different by issuing a
cmpb and shifts the result based on its output:
leadzero = (__builtin_ffsl (z1) - 1);
leadzero = leadzero > (n-1)*8 ? (n-1)*8 : leadzero;
r1 = (r1 >> leadzero) & 0xFFUL;
r2 = (r2 >> leadzero) & 0xFFUL;
return r1 - r2; */
.align 4
L(different1):
neg r11, r8
sldi r5, r5, 3
and r8, r11, r8
addi r5, r5, -8
cntlzd r8, r8
subfic r8, r8, 63
extsw r8, r8
cmpld cr7, r8, r5
ble cr7, L(different2)
mr r8, r5
L(different2):
extsw r8, r8
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 r5, r5, -1
subf r7, r8, r5
subf r9, r7, r5
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 r5, r5, -1
cmplw cr7, r9, r8
cmpdi cr5, r9, 0
bne cr7, L(byte_ne_2)
beq cr5, L(byte_ne_0)
L(pagecross_loop1):
cmpdi cr7, r5, 0
addi r3, r3, 1
addi r4, r4, 1
bdnz L(pagecross_loop0)
cmpdi cr7, r7, 0
li r9, 0
bne+ cr7, L(align)
b L(ret1)
.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(byte_ne_3):
extsw r7, r7
b L(byte_ne_1)
END(STRNCMP)
libc_hidden_builtin_def(strncmp)
|
