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/* Optimized strcmp implementation for PowerPC64/POWER9.
Copyright (C) 2016-2021 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>
#ifndef STRCMP
# define STRCMP strcmp
#endif
/* Implements the function
int [r3] strcmp (const char *s1 [r3], const char *s2 [r4])
The implementation uses unaligned doubleword access for first 32 bytes
as in POWER8 patch and uses vectorised loops after that. */
/* 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: \
addi r6, reg2, 16; \
lvx v9, 0, r6; \
2: \
vperm reg1, v9, reg1, reg3;
/* TODO: change this to .machine power9 when the minimum required binutils
allows it. */
.machine power7
ENTRY_TOCLESS (STRCMP, 4)
li r0, 0
/* 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 r7, r3, 0, 52
rldicl r9, r4, 0, 52
cmpldi cr7, r7, 4096-16
bgt cr7, L(pagecross_check)
cmpldi cr5, r9, 4096-16
bgt cr5, L(pagecross_check)
/* For short strings up to 16 bytes, load both s1 and s2 using
unaligned dwords and compare. */
ld r8, 0(r3)
ld r10, 0(r4)
cmpb r12, r8, r0
cmpb r11, r8, r10
orc. r9, r12, r11
bne cr0, L(different_nocmpb)
ld r8, 8(r3)
ld r10, 8(r4)
cmpb r12, r8, r0
cmpb r11, r8, r10
orc. r9, r12, r11
bne cr0, L(different_nocmpb)
addi r7, r3, 16
addi r4, r4, 16
L(align):
/* Now it has checked for first 16 bytes. */
vspltisb v0, 0
vspltisb v2, -1
lvsr v6, 0, r4 /* Compute mask. */
or r5, r4, r7
andi. r5, r5, 0xF
beq cr0, L(aligned)
andi. r5, r7, 0xF
beq cr0, L(s1_align)
lvsr v10, 0, r7 /* Compute mask. */
/* Both s1 and s2 are unaligned. */
GET16BYTES(v4, r7, v10)
GET16BYTES(v5, r4, v6)
VCMPNEZB(v7, v5, v4)
beq cr6, L(match)
b L(different)
/* Align s1 to qw and adjust s2 address. */
.align 4
L(match):
clrldi r6, r7, 60
subfic r5, r6, 16
add r7, r7, r5
add r4, r4, r5
andi. r5, r4, 0xF
beq cr0, L(aligned)
lvsr v6, 0, r4
/* There are 2 loops depending on the input alignment.
Each loop gets 16 bytes from s1 and s2 and compares.
Loop until a mismatch or null occurs. */
L(s1_align):
lvx v4, r7, r0
GET16BYTES(v5, r4, v6)
VCMPNEZB(v7, v5, v4)
addi r7, r7, 16
addi r4, r4, 16
bne cr6, L(different)
lvx v4, r7, r0
GET16BYTES(v5, r4, v6)
VCMPNEZB(v7, v5, v4)
addi r7, r7, 16
addi r4, r4, 16
bne cr6, L(different)
lvx v4, r7, r0
GET16BYTES(v5, r4, v6)
VCMPNEZB(v7, v5, v4)
addi r7, r7, 16
addi r4, r4, 16
bne cr6, L(different)
lvx v4, r7, r0
GET16BYTES(v5, r4, v6)
VCMPNEZB(v7, v5, v4)
addi r7, r7, 16
addi r4, r4, 16
beq cr6, L(s1_align)
b L(different)
.align 4
L(aligned):
lvx v4, 0, r7
lvx v5, 0, r4
VCMPNEZB(v7, v5, v4)
addi r7, r7, 16
addi r4, r4, 16
bne cr6, L(different)
lvx v4, 0, r7
lvx v5, 0, r4
VCMPNEZB(v7, v5, v4)
addi r7, r7, 16
addi r4, r4, 16
bne cr6, L(different)
lvx v4, 0, r7
lvx v5, 0, r4
VCMPNEZB(v7, v5, v4)
addi r7, r7, 16
addi r4, r4, 16
bne cr6, L(different)
lvx v4, 0, r7
lvx v5, 0, r4
VCMPNEZB(v7, v5, v4)
addi r7, r7, 16
addi r4, r4, 16
beq cr6, L(aligned)
/* Calculate and return the difference. */
L(different):
VCTZLSBB(r6, v7)
VEXTUBRX(r5, r6, v4)
VEXTUBRX(r4, r6, v5)
subf r3, r4, r5
extsw r3, r3
blr
.align 4
L(different_nocmpb):
neg r3, r9
and r9, r9, r3
cntlzd r9, r9
subfic r9, r9, 63
srd r3, r8, r9
srd r10, r10, r9
rldicl r10, r10, 0, 56
rldicl r3, r3, 0, 56
subf r3, r10, r3
extsw r3, r3
blr
.align 4
L(pagecross_check):
subfic r9, r9, 4096
subfic r7, r7, 4096
cmpld cr7, r7, r9
bge cr7, L(pagecross)
mr r7, r9
/* 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. */
L(pagecross):
add r7, r3, r7
subf r9, r3, r7
mtctr r9
.align 4
L(pagecross_loop):
/* Loads a byte from s1 and s2, compare if *s1 is equal to *s2
and if *s1 is '\0'. */
lbz r9, 0(r3)
lbz r10, 0(r4)
addi r3, r3, 1
addi r4, r4, 1
cmplw cr7, r9, r10
cmpdi cr5, r9, r0
bne cr7, L(pagecross_ne)
beq cr5, L(pagecross_nullfound)
bdnz L(pagecross_loop)
b L(align)
.align 4
L(pagecross_ne):
extsw r3, r9
mr r9, r10
L(pagecross_retdiff):
subf r9, r9, r3
extsw r3, r9
blr
.align 4
L(pagecross_nullfound):
li r3, 0
b L(pagecross_retdiff)
END (STRCMP)
libc_hidden_builtin_def (strcmp)
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