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/* Optimized memchr implementation for POWER8.
Copyright (C) 2017 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>
/* void *[r3] memchr (const void *s [r3], int c [r4], size_t n [r5]) */
/* TODO: change these to the actual instructions when the minimum required
binutils allows it. */
#define MTVRD(v, r) .long (0x7c000167 | ((v)<<(32-11)) | ((r)<<(32-16)))
#define MFVRD(r, v) .long (0x7c000067 | ((v)<<(32-11)) | ((r)<<(32-16)))
#define VBPERMQ(t, a, b) .long (0x1000054c \
| ((t)<<(32-11)) \
| ((a)<<(32-16)) \
| ((b)<<(32-21)) )
#ifndef MEMCHR
# define MEMCHR __memchr
#endif
/* TODO: change this to .machine power8 when the minimum required binutils
allows it. */
.machine power7
ENTRY_TOCLESS (MEMCHR)
CALL_MCOUNT 3
dcbt 0, r3
clrrdi r8, r3, 3
insrdi r4, r4, 8, 48
/* Calculate the last acceptable address and check for possible
addition overflow by using satured math:
r7 = r3 + r5
r7 |= -(r7 < x) */
add r7, r3, r5
subfc r6, r3, r7
subfe r9, r9, r9
extsw r6, r9
or r7, r7, r6
insrdi r4, r4, 16, 32
cmpldi r5, 32
li r9, -1
rlwinm r6, r3, 3, 26, 28 /* Calculate padding. */
insrdi r4, r4, 32, 0
mr r10, r7
addi r7, r7, -1
#ifdef __LITTLE_ENDIAN__
sld r9, r9, r6
#else
srd r9, r9, r6
#endif
ble L(small_range)
andi. r11, r3, 63
beq cr0, L(align_qw)
clrldi r11, r3, 61
ld r12, 0(r8) /* Load doubleword from memory. */
cmpb r3, r12, r4 /* Check for BYTEs in DWORD1. */
and r3, r3, r9
clrldi r6, r7, 61 /* Byte count - 1 in last dword. */
clrrdi r7, r7, 3 /* Address of last doubleword. */
cmpldi cr7, r3, 0 /* Does r3 indicate we got a hit? */
bne cr7, L(done)
addi r8, r8, 8
addi r5, r5, -8
add r5, r5, r11
/* Are we now aligned to a quadword boundary? */
andi. r11, r8, 15
beq cr0, L(align_qw)
/* Handle DWORD to make it QW aligned. */
ld r12, 0(r8)
cmpb r3, r12, r4
cmpldi cr7, r3, 0
bne cr7, L(done)
addi r5, r5, -8
addi r8, r8, 8
/* At this point, r8 is 16B aligned. */
L(align_qw):
vspltisb v0, 0
/* Precompute vbpermq constant. */
vspltisb v10, 3
li r0, 0
lvsl v11, r0, r0
vslb v10, v11, v10
MTVRD(v1, r4)
vspltb v1, v1, 7
cmpldi r5, 64
ble L(tail64)
/* Are we 64-byte aligned? If so, jump to the vectorized loop.
Note: aligning to 64-byte will necessarily slow down performance for
strings around 64 bytes in length due to the extra comparisons
required to check alignment for the vectorized loop. This is a
necessary tradeoff we are willing to take in order to speed up the
calculation for larger strings. */
andi. r11, r8, 63
beq cr0, L(preloop_64B)
/* In order to begin the 64B loop, it needs to be 64
bytes aligned. So read until it is 64B aligned. */
lvx v4, 0, r8
vcmpequb v6, v1, v4
vcmpequb. v11, v0, v6
bnl cr6, L(found_16B)
addi r8, r8, 16
addi r5, r5, -16
andi. r11, r8, 63
beq cr0, L(preloop_64B)
lvx v4, 0, r8
vcmpequb v6, v1, v4
vcmpequb. v11, v0, v6
bnl cr6, L(found_16B)
addi r8, r8, 16
addi r5, r5, -16
andi. r11, r8, 63
beq cr0, L(preloop_64B)
lvx v4, 0, r8
vcmpequb v6, v1, v4
vcmpequb. v11, v0, v6
bnl cr6, L(found_16B)
addi r8, r8, 16
addi r5, r5, -16
/* At this point it should be 64B aligned.
Prepare for the 64B loop. */
L(preloop_64B):
cmpldi r5, 64 /* Check if r5 < 64. */
ble L(tail64)
sub r6, r10, r8
srdi r9, r6, 6 /* Number of loop iterations. */
mtctr r9 /* Setup the counter. */
li r11, 16 /* Load required offsets. */
li r9, 32
li r7, 48
/* Handle r5 > 64. Loop over the bytes in strides of 64B. */
.align 4
L(loop):
lvx v2, 0, r8 /* Load 4 quadwords. */
lvx v3, r8, r11
lvx v4, v8, r9
lvx v5, v8, r7
vcmpequb v6, v1, v2
vcmpequb v7, v1, v3
vcmpequb v8, v1, v4
vcmpequb v9, v1, v5
vor v11, v6, v7
vor v12, v8, v9
vor v11, v11, v12 /* Compare and merge into one VR for speed. */
vcmpequb. v11, v0, v11
bnl cr6, L(found)
addi r8, r8, 64 /* Adjust address for the next iteration. */
bdnz L(loop)
clrldi r5, r6, 58
/* Handle remainder of 64B loop or r5 > 64. */
.align 4
L(tail64):
cmpldi r5, 0
beq L(null)
lvx v4, 0, r8
vcmpequb v6, v1, v4
vcmpequb. v11, v0, v6
bnl cr6, L(found_16B)
addi r8, r8, 16
cmpldi cr6, r5, 16
ble cr6, L(null)
addi r5, r5, -16
lvx v4, 0, r8
vcmpequb v6, v1, v4
vcmpequb. v11, v0, v6
bnl cr6, L(found_16B)
addi r8, r8, 16
cmpldi cr6, r5, 16
ble cr6, L(null)
addi r5, r5, -16
lvx v4, 0, r8
vcmpequb v6, v1, v4
vcmpequb. v11, v0, v6
bnl cr6, L(found_16B)
addi r8, r8, 16
cmpldi cr6, r5, 16
ble cr6, L(null)
addi r5, r5, -16
lvx v4, 0, r8
vcmpequb v6, v1, v4
vcmpequb. v11, v0, v6
bnl cr6, L(found_16B)
li r3, 0
blr
/* Found a match in 64B loop. */
.align 4
L(found):
/* Permute the first bit of each byte into bits 48-63. */
VBPERMQ(v6, v6, v10)
VBPERMQ(v7, v7, v10)
VBPERMQ(v8, v8, v10)
VBPERMQ(v9, v9, v10)
/* Shift each component into its correct position for merging. */
#ifdef __LITTLE_ENDIAN__
vsldoi v7, v7, v7, 2
vsldoi v8, v8, v8, 4
vsldoi v9, v9, v9, 6
#else
vsldoi v6, v6, v6, 6
vsldoi v7, v7, v7, 4
vsldoi v8, v8, v8, 2
#endif
/* Merge the results and move to a GPR. */
vor v11, v6, v7
vor v4, v9, v8
vor v4, v11, v4
MFVRD(r5, v4)
#ifdef __LITTLE_ENDIAN__
addi r6, r5, -1
andc r6, r6, r5
popcntd r6, r6
#else
cntlzd r6, r5 /* Count leading zeros before the match. */
#endif
add r3, r8, r6 /* Compute final length. */
blr
/* Found a match in last 16 bytes. */
.align 4
L(found_16B):
/* Permute the first bit of each byte into bits 48-63. */
VBPERMQ(v6, v6, v10)
/* Shift each component into its correct position for merging. */
#ifdef __LITTLE_ENDIAN__
MFVRD(r7, v6)
addi r6, r7, -1
andc r6, r6, r7
popcntd r6, r6
#else
vsldoi v6, v6, v6, 6
MFVRD(r7, v6)
cntlzd r6, r7 /* Count leading zeros before the match. */
#endif
add r3, r8, r6 /* Compute final length. */
cmpld r6, r5
bltlr
li r3, 0
blr
.align 4
/* r3 has the output of the cmpb instruction, that is, it contains
0xff in the same position as BYTE in the original
doubleword from the string. Use that to calculate the pointer.
We need to make sure BYTE is *before* the end of the range. */
L(done):
#ifdef __LITTLE_ENDIAN__
addi r0, r3, -1
andc r0, r0, r3
popcntd r0, r0 /* Count trailing zeros. */
#else
cntlzd r0, r3 /* Count leading zeros before the match. */
#endif
cmpld r8, r7 /* Are we on the last dword? */
srdi r0, r0, 3 /* Convert leading/trailing zeros to bytes. */
add r3, r8, r0
cmpld cr7, r0, r6 /* If on the last dword, check byte offset. */
bnelr
blelr cr7
li r3, 0
blr
.align 4
L(null):
li r3, 0
blr
/* Deals with size <= 32. */
.align 4
L(small_range):
cmpldi r5, 0
beq L(null)
ld r12, 0(r8) /* Load word from memory. */
cmpb r3, r12, r4 /* Check for BYTE in DWORD1. */
and r3, r3, r9
cmpldi cr7, r3, 0
clrldi r6, r7, 61 /* Byte count - 1 in last dword. */
clrrdi r7, r7, 3 /* Address of last doubleword. */
cmpld r8, r7 /* Are we done already? */
bne cr7, L(done)
beqlr
ldu r12, 8(r8)
cmpb r3, r12, r4
cmpldi cr6, r3, 0
cmpld r8, r7
bne cr6, L(done) /* Found something. */
beqlr /* Hit end of string (length). */
ldu r12, 8(r8)
cmpb r3, r12, r4
cmpldi cr6, r3, 0
cmpld r8, r7
bne cr6, L(done)
beqlr
ldu r12, 8(r8)
cmpb r3, r12, r4
cmpldi cr6, r3, 0
cmpld r8, r7
bne cr6, L(done)
beqlr
ldu r12, 8(r8)
cmpb r3, r12, r4
cmpldi cr6, r3, 0
bne cr6, L(done)
blr
END (MEMCHR)
weak_alias (__memchr, memchr)
libc_hidden_builtin_def (memchr)
|
