mirror of
https://sourceware.org/git/glibc.git
synced 2024-11-27 15:30:07 +00:00
688903eb3e
* All files with FSF copyright notices: Update copyright dates using scripts/update-copyrights. * locale/programs/charmap-kw.h: Regenerated. * locale/programs/locfile-kw.h: Likewise.
426 lines
14 KiB
ArmAsm
426 lines
14 KiB
ArmAsm
/* Optimized strnlen implementation for POWER8 using a vmx loop.
|
|
|
|
Copyright (C) 2017-2018 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/>. */
|
|
|
|
/* It is implemented the following heuristic:
|
|
1. Case maxlen <= 32: align the pointer to 8 bytes to loop through
|
|
reading doublewords. Uses the POWER7 algorithm.
|
|
2. Case maxlen > 32: check for null bytes in the first 16 bytes using
|
|
unaligned accesses. Return length if found. Otherwise:
|
|
2.1 Case maxlen < 64: deduct the bytes previously read, align
|
|
the pointer to 16 bytes and loop through reading quadwords
|
|
until find null bytes or reach maxlen.
|
|
2.2 Case maxlen > 64: deduct the bytes previously read, align
|
|
the pointer to 64 bytes and set up a counter to loop through
|
|
reading in strides of 64 bytes. In case it finished the loop
|
|
with null bytes not found, process the remainder bytes by
|
|
switching to the loop to heuristic in 2.1. */
|
|
|
|
#include <sysdep.h>
|
|
|
|
/* Define default page size to 4KB. */
|
|
#define PAGE_SIZE 4096
|
|
|
|
/* The following macros implement Power ISA v2.07 opcodes
|
|
that could not be used directly into this code to the keep
|
|
compatibility with older binutils versions. */
|
|
|
|
/* Move from vector register doubleword. */
|
|
#define MFVRD(r,v) .long (0x7c000067 | ((v)<<(32-11)) | ((r)<<(32-16)))
|
|
|
|
/* Move to vector register doubleword. */
|
|
#define MTVRD(v,r) .long (0x7c000167 | ((v)<<(32-11)) | ((r)<<(32-16)))
|
|
|
|
/* Vector Bit Permute Quadword. */
|
|
#define VBPERMQ(t,a,b) .long (0x1000054c \
|
|
| ((t)<<(32-11)) \
|
|
| ((a)<<(32-16)) \
|
|
| ((b)<<(32-21)) )
|
|
|
|
/* Vector Population Count Halfword. */
|
|
#define VPOPCNTH(t,b) .long (0x10000743 | ((t)<<(32-11)) | ((b)<<(32-21)))
|
|
|
|
/* Vector Count Leading Zeros Halfword. */
|
|
#define VCLZH(t,b) .long (0x10000742 | ((t)<<(32-11)) | ((b)<<(32-21)))
|
|
|
|
|
|
/* int [r3] strnlen (char *s [r3], size_t maxlen [r4]) */
|
|
/* TODO: change to power8 when minimum required binutils allows it. */
|
|
.machine power7
|
|
ENTRY_TOCLESS (__strnlen)
|
|
CALL_MCOUNT 2
|
|
dcbt 0,r3
|
|
|
|
cmpldi r4,32 /* Check if maxlen <= 32. */
|
|
ble L(small_range) /* If maxlen <= 32. */
|
|
|
|
/* Upcoming 16 bytes unaligned accesses cannot cross the page boundary
|
|
otherwise the processor throws an memory access error.
|
|
Use following code to check there is room for such as accesses:
|
|
(((size_t) s) % PAGE_SIZE > (PAGE_SIZE - 16)
|
|
If it is disallowed then switch to the code that handles
|
|
the string when maxlen <= 32. */
|
|
clrldi r10,r3,52
|
|
cmpldi cr7,r10,PAGE_SIZE-16
|
|
bgt cr7,L(small_range) /* If less than 16B of page end. */
|
|
|
|
/* Compute our permute constant r8. */
|
|
li r7,0
|
|
/* Compute a bpermd constant to move bit 0 of each word into
|
|
a halfword value, and count trailing zeros. */
|
|
#ifdef __LITTLE_ENDIAN__
|
|
li r8,0x2820
|
|
oris r8,r8,0x3830
|
|
sldi r8,r8,32
|
|
ori r8,r8,0x0800
|
|
oris r8,r8,0x1810
|
|
#else
|
|
li r8,0x1018
|
|
oris r8,r8,0x0008
|
|
sldi r8,r8,32
|
|
ori r8,r8,0x3038
|
|
oris r8,r8,0x2028
|
|
#endif
|
|
|
|
/* maxlen > 32. Optimistically check for null bytes in the first
|
|
16 bytes of the string using unaligned accesses. */
|
|
ld r5,0(r3)
|
|
ld r6,8(r3)
|
|
cmpb r10,r7,r5 /* Check for null bytes in DWORD1. */
|
|
cmpb r11,r7,r6 /* Check for null bytes in DWORD2. */
|
|
or. r7,r10,r11
|
|
bne cr0, L(early_find) /* If found null bytes. */
|
|
|
|
/* At this point maxlen > 32 and null bytes were not found at first
|
|
16 bytes. Prepare for loop using VMX. */
|
|
|
|
/* r3 == s, r4 == maxlen. All other volatile regs are unused now. */
|
|
|
|
addi r5,r3,16 /* Align up, or just add the 16B we
|
|
already checked. */
|
|
li r0,15
|
|
and r7,r5,r0 /* Find offset into 16B alignment. */
|
|
andc r5,r5,r0 /* Quadword align up s to the next quadword. */
|
|
li r0,16
|
|
subf r0,r7,r0
|
|
subf r4,r0,r4 /* Deduct unaligned bytes from maxlen. */
|
|
|
|
|
|
/* Compute offsets for vmx loads, and precompute the vbpermq
|
|
constants for both the 64B and 16B loops. */
|
|
li r6,0
|
|
vspltisb v0,0
|
|
vspltisb v10,3
|
|
lvsl v11,r6,r6
|
|
vslb v10,v11,v10
|
|
|
|
cmpldi r4,64 /* Check maxlen < 64. */
|
|
blt L(smaller) /* If maxlen < 64 */
|
|
|
|
/* In order to begin the 64B loop, it needs to be 64
|
|
bytes aligned. So read quadwords until it is aligned or found null
|
|
bytes. At worst case it will be aligned after the fourth iteration,
|
|
so unroll the loop to avoid counter checking. */
|
|
andi. r7,r5,63 /* Check if is 64 bytes aligned. */
|
|
beq cr0,L(preloop_64B) /* If it is already 64B aligned. */
|
|
lvx v1,r5,r6
|
|
vcmpequb. v1,v1,v0
|
|
addi r5,r5,16
|
|
addi r4,r4,-16 /* Decrement maxlen in 16 bytes. */
|
|
bne cr6,L(found_aligning64B) /* If found null bytes. */
|
|
|
|
/* Unroll 2x above code block until aligned or find null bytes. */
|
|
andi. r7,r5,63
|
|
beq cr0,L(preloop_64B)
|
|
lvx v1,r5,r6
|
|
vcmpequb. v1,v1,v0
|
|
addi r5,r5,16
|
|
addi r4,r4,-16
|
|
bne cr6,L(found_aligning64B)
|
|
|
|
andi. r7,r5,63
|
|
beq cr0,L(preloop_64B)
|
|
lvx v1,r5,r6
|
|
vcmpequb. v1,v1,v0
|
|
addi r5,r5,16
|
|
addi r4,r4,-16
|
|
bne cr6,L(found_aligning64B)
|
|
|
|
/* At this point it should be 16 bytes aligned.
|
|
Prepare for the 64B loop. */
|
|
.p2align 4
|
|
L(preloop_64B):
|
|
/* Check if maxlen became is less than 64, therefore disallowing the
|
|
64B loop. If it happened switch to the 16B loop code. */
|
|
cmpldi r4,64 /* Check if maxlen < 64. */
|
|
blt L(smaller) /* If maxlen < 64. */
|
|
/* Set some constant values. */
|
|
li r7,16
|
|
li r10,32
|
|
li r9,48
|
|
|
|
/* Compute the number of 64 bytes iterations needed. */
|
|
srdi r11,r4,6 /* Compute loop count (maxlen / 64). */
|
|
andi. r4,r4,63 /* Set maxlen the remainder (maxlen % 64). */
|
|
mtctr r11 /* Move loop count to counter register. */
|
|
|
|
/* Handle maxlen > 64. Loop over the bytes in strides of 64B. */
|
|
.p2align 4
|
|
L(loop_64B):
|
|
lvx v1,r5,r6 /* r5 is the pointer to s. */
|
|
lvx v2,r5,r7
|
|
lvx v3,r5,r10
|
|
lvx v4,r5,r9
|
|
/* Compare the four 16B vectors to obtain the least 16 values.
|
|
Null bytes should emerge into v7, then check for null bytes. */
|
|
vminub v5,v1,v2
|
|
vminub v6,v3,v4
|
|
vminub v7,v5,v6
|
|
vcmpequb. v7,v7,v0 /* Check for null bytes. */
|
|
addi r5,r5,64 /* Add pointer to next iteraction. */
|
|
bne cr6,L(found_64B) /* If found null bytes. */
|
|
bdnz L(loop_64B) /* Continue the loop if count > 0. */
|
|
|
|
/* Hit loop end without null match. So branch to handle the remainder. */
|
|
|
|
/* Prepare a 16B loop to handle two cases:
|
|
1. If 32 > maxlen < 64.
|
|
2. If maxlen >= 64, and reached end of the 64B loop with null
|
|
bytes not found. Thus handle the remainder bytes here. */
|
|
.p2align 4
|
|
L(smaller):
|
|
cmpldi r4,0 /* Check maxlen is zero. */
|
|
beq L(done) /* If maxlen is zero. */
|
|
|
|
/* Place rounded up number of qw's to check into a vmx
|
|
register, and use some vector tricks to minimize
|
|
branching. */
|
|
MTVRD(v7,r4) /* Copy maxlen from GPR to vector register. */
|
|
vspltisb v5,1
|
|
vspltisb v6,15
|
|
vspltb v2,v7,7
|
|
vaddubs v3,v5,v6
|
|
|
|
#ifdef __LITTLE_ENDIAN__
|
|
vspltish v5,1 /* Compute 16 in each byte. */
|
|
#endif
|
|
|
|
/* Loop in 16B aligned incremements now. */
|
|
.p2align 4
|
|
L(loop_16B):
|
|
lvx v1,r5,r6 /* Load quadword into vector register. */
|
|
addi r5,r5,16 /* Increment address to next 16B block. */
|
|
vor v7,v2,v2 /* Save loop count (v2) into v7. */
|
|
vsububs v2,v2,v3 /* Subtract 16B from count, saturate at 0. */
|
|
vminub v4,v1,v2
|
|
vcmpequb. v4,v4,v0 /* Checking for null bytes. */
|
|
beq cr6,L(loop_16B) /* If null bytes not found. */
|
|
|
|
vcmpequb v1,v1,v0
|
|
VBPERMQ(v1,v1,v10)
|
|
#ifdef __LITTLE_ENDIAN__
|
|
vsubuhm v2,v1,v5 /* Form a mask of trailing zeros. */
|
|
vandc v2,v2,v1
|
|
VPOPCNTH(v1,v2) /* Count of trailing zeros, 16 if none. */
|
|
#else
|
|
VCLZH(v1,v1) /* Count the leading zeros, 16 if none. */
|
|
#endif
|
|
/* Truncate to maximum allowable offset. */
|
|
vcmpgtub v2,v1,v7 /* Compare and truncate for matches beyond
|
|
maxlen. */
|
|
vsel v1,v1,v7,v2 /* 0-16 is now in byte 7. */
|
|
|
|
MFVRD(r0,v1)
|
|
addi r5,r5,-16 /* Undo speculative bump. */
|
|
extsb r0,r0 /* Clear whatever gunk is in the high 56b. */
|
|
add r5,r5,r0 /* Add the offset of whatever was found. */
|
|
L(done):
|
|
subf r3,r3,r5 /* Length is equal to the offset of null byte
|
|
matched minus the pointer to s. */
|
|
blr /* Done. */
|
|
|
|
/* Handle case of maxlen > 64 and found null bytes in last block
|
|
of 64 bytes read. */
|
|
.p2align 4
|
|
L(found_64B):
|
|
/* A zero was found. Reduce the result. */
|
|
vcmpequb v1,v1,v0
|
|
vcmpequb v2,v2,v0
|
|
vcmpequb v3,v3,v0
|
|
vcmpequb v4,v4,v0
|
|
|
|
/* Permute the first bit of each byte into bits 48-63. */
|
|
VBPERMQ(v1,v1,v10)
|
|
VBPERMQ(v2,v2,v10)
|
|
VBPERMQ(v3,v3,v10)
|
|
VBPERMQ(v4,v4,v10)
|
|
|
|
/* Shift each component into its correct position for merging. */
|
|
#ifdef __LITTLE_ENDIAN__
|
|
vsldoi v2,v2,v2,2
|
|
vsldoi v3,v3,v3,4
|
|
vsldoi v4,v4,v4,6
|
|
#else
|
|
vsldoi v1,v1,v1,6
|
|
vsldoi v2,v2,v2,4
|
|
vsldoi v3,v3,v3,2
|
|
#endif
|
|
|
|
/* Merge the results and move to a GPR. */
|
|
vor v1,v2,v1
|
|
vor v2,v3,v4
|
|
vor v4,v1,v2
|
|
|
|
/* Adjust address to the start of the current 64B block. */
|
|
addi r5,r5,-64
|
|
|
|
MFVRD(r10,v4)
|
|
#ifdef __LITTLE_ENDIAN__
|
|
addi r9,r10,-1 /* Form a mask from trailing zeros. */
|
|
andc r9,r9,r10
|
|
popcntd r0,r9 /* Count the bits in the mask. */
|
|
#else
|
|
cntlzd r0,r10 /* Count leading zeros before the match. */
|
|
#endif
|
|
subf r5,r3,r5
|
|
add r3,r5,r0 /* Compute final length. */
|
|
blr /* Done. */
|
|
|
|
/* Handle case where null bytes were found while aligning
|
|
as a preparation for the 64B loop. */
|
|
.p2align 4
|
|
L(found_aligning64B):
|
|
VBPERMQ(v1,v1,v10)
|
|
#ifdef __LITTLE_ENDIAN__
|
|
MFVRD(r10,v1)
|
|
addi r9,r10,-1 /* Form a mask from trailing zeros. */
|
|
andc r9,r9,r10
|
|
popcntd r0,r9 /* Count the bits in the mask. */
|
|
#else
|
|
vsldoi v1,v1,v1,6
|
|
MFVRD(r10,v1)
|
|
cntlzd r0,r10 /* Count leading zeros before the match. */
|
|
#endif
|
|
addi r5,r5,-16 /* Adjust address to offset of last 16 bytes
|
|
read. */
|
|
/* Calculate length as subtracted the pointer to s of last 16 bytes
|
|
offset, added with the bytes before the match. */
|
|
subf r5,r3,r5
|
|
add r3,r5,r0
|
|
blr /* Done. */
|
|
|
|
/* Handle case of maxlen > 32 and found a null bytes within the first
|
|
16 bytes of s. */
|
|
.p2align 4
|
|
L(early_find):
|
|
bpermd r5,r8,r10 /* r8 contains the bit permute constants. */
|
|
bpermd r6,r8,r11
|
|
sldi r5,r5,8
|
|
or r5,r5,r6 /* r5 should hold a 16B mask of
|
|
a potential 0. */
|
|
cntlzd r5,r5 /* Count leading zeros. */
|
|
addi r3,r5,-48 /* Deduct the 48 leading zeros always
|
|
present. */
|
|
blr /* Done. */
|
|
|
|
/* Handle case of maxlen <= 32. Use the POWER7 algorithm. */
|
|
.p2align 4
|
|
L(small_range):
|
|
clrrdi r8,r3,3 /* Align the pointer to 8B. */
|
|
li r0,0
|
|
/* Register's content at this point:
|
|
r3 == pointer to s, r4 == maxlen, r8 == pointer to s aligned to 8B,
|
|
r7 == last acceptable address. */
|
|
cmpldi r4,0 /* Check if maxlen is zero. */
|
|
beq L(end_max) /* If maxlen is zero. */
|
|
|
|
/* Calculate the last acceptable address and check for possible
|
|
addition overflow by using satured math:
|
|
r7 = r3 + r4
|
|
r7 |= -(r7 < x) */
|
|
add r7,r3,r4
|
|
subfc r6,r3,r7
|
|
subfe r9,r9,r9
|
|
extsw r6,r9
|
|
or r7,r7,r6
|
|
addi r7,r7,-1
|
|
|
|
clrrdi r7,r7,3 /* Align to 8B address of last
|
|
acceptable address. */
|
|
|
|
rlwinm r6,r3,3,26,28 /* Calculate padding. */
|
|
ld r12,0(r8) /* Load aligned doubleword. */
|
|
cmpb r10,r12,r0 /* Check for null bytes. */
|
|
#ifdef __LITTLE_ENDIAN__
|
|
srd r10,r10,r6
|
|
sld r10,r10,r6
|
|
#else
|
|
sld r10,r10,r6
|
|
srd r10,r10,r6
|
|
#endif /* __LITTLE_ENDIAN__ */
|
|
cmpldi cr7,r10,0
|
|
bne cr7,L(done_small) /* If found null byte. */
|
|
|
|
cmpld r8,r7 /* Check if reached maxlen. */
|
|
beq L(end_max) /* If reached maxlen. */
|
|
|
|
/* Still handling case of maxlen <= 32. Read doubleword aligned until
|
|
find null bytes or reach maxlen. */
|
|
.p2align 4
|
|
L(loop_small):
|
|
ldu r12,8(r8) /* Load next doubleword and update r8. */
|
|
cmpb r10,r12,r0 /* Check for null bytes. */
|
|
cmpldi cr6,r10,0
|
|
bne cr6,L(done_small) /* If found null bytes. */
|
|
cmpld r8,r7 /* Check if reached maxlen. */
|
|
bne L(loop_small) /* If it has more bytes to read. */
|
|
mr r3,r4 /* Reached maxlen with null bytes not found.
|
|
Length is equal to maxlen. */
|
|
blr /* Done. */
|
|
|
|
/* Still handling case of maxlen <= 32. Found null bytes.
|
|
Registers: r10 == match bits within doubleword, r8 == address of
|
|
last doubleword read, r3 == pointer to s, r4 == maxlen. */
|
|
.p2align 4
|
|
L(done_small):
|
|
#ifdef __LITTLE_ENDIAN__
|
|
/* Count trailing zeros. */
|
|
addi r0,r10,-1
|
|
andc r0,r0,r10
|
|
popcntd r0,r0
|
|
#else
|
|
cntlzd r0,r10 /* Count leading zeros before the match. */
|
|
#endif
|
|
sub r3,r8,r3 /* Calculate total of bytes before the match. */
|
|
srdi r0,r0,3 /* Convert leading/trailing zeros to bytes. */
|
|
add r3,r3,r0 /* Length until the match. */
|
|
cmpld r3,r4 /* Check length is greater than maxlen. */
|
|
blelr
|
|
mr r3,r4 /* If length is greater than maxlen, return
|
|
maxlen. */
|
|
blr
|
|
|
|
/* Handle case of reached maxlen with null bytes not found. */
|
|
.p2align 4
|
|
L(end_max):
|
|
mr r3,r4 /* Length is equal to maxlen. */
|
|
blr /* Done. */
|
|
|
|
|
|
END (__strnlen)
|
|
libc_hidden_def (__strnlen)
|
|
weak_alias (__strnlen, strnlen)
|
|
libc_hidden_def (strnlen)
|