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Merge "libc: import ARM strcmp from newlib"

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This commit is contained in:
Haibo Huang 2019-05-16 19:28:11 +00:00 committed by Gerrit Code Review
commit b43f0b7993
6 changed files with 441 additions and 1348 deletions
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2
libc/Android.bp
View file

@ -790,13 +790,11 @@ cc_library_static {
"arch-arm/cortex-a9/bionic/memset.S",
"arch-arm/cortex-a9/bionic/stpcpy.S",
"arch-arm/cortex-a9/bionic/strcat.S",
"arch-arm/cortex-a9/bionic/strcmp.S",
"arch-arm/cortex-a9/bionic/strcpy.S",
"arch-arm/cortex-a9/bionic/strlen.S",
"arch-arm/krait/bionic/memcpy.S",
"arch-arm/krait/bionic/memset.S",
"arch-arm/krait/bionic/strcmp.S",
"arch-arm/cortex-a53/bionic/memcpy.S",

28
libc/NOTICE
View file

@ -5330,6 +5330,34 @@ Copyright (c) 2012-2013, Linaro Limited
-------------------------------------------------------------------
Copyright (c) 2012-2014 ARM Ltd
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
1. Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
3. The name of the company may not be used to endorse or promote
products derived from this software without specific prior written
permission.
THIS SOFTWARE IS PROVIDED BY ARM LTD ``AS IS'' AND ANY EXPRESS OR IMPLIED
WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
IN NO EVENT SHALL ARM LTD BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-------------------------------------------------------------------
Copyright (c) 2013
MIPS Technologies, Inc., California.

708
libc/arch-arm/cortex-a15/bionic/strcmp.S
View file

@ -1,5 +1,5 @@
/*
* Copyright (c) 2013 ARM Ltd
* Copyright (c) 2012-2014 ARM Ltd
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
@ -29,9 +29,9 @@
#include <private/bionic_asm.h>
#ifdef __ARMEB__
#define S2LOMEM lsl
#define S2LOMEMEQ lsleq
#define S2HIMEM lsr
#define S2LO lsl
#define S2LOEQ lsleq
#define S2HI lsr
#define MSB 0x000000ff
#define LSB 0xff000000
#define BYTE0_OFFSET 24
@ -39,9 +39,9 @@
#define BYTE2_OFFSET 8
#define BYTE3_OFFSET 0
#else /* not __ARMEB__ */
#define S2LOMEM lsr
#define S2LOMEMEQ lsreq
#define S2HIMEM lsl
#define S2LO lsr
#define S2LOEQ lsreq
#define S2HI lsl
#define BYTE0_OFFSET 0
#define BYTE1_OFFSET 8
#define BYTE2_OFFSET 16
@ -50,330 +50,446 @@
#define LSB 0x000000ff
#endif /* not __ARMEB__ */
.syntax unified
/* Parameters and result. */
#define src1 r0
#define src2 r1
#define result r0 /* Overlaps src1. */
#if defined (__thumb__)
.thumb
.thumb_func
#endif
/* Internal variables. */
#define tmp1 r4
#define tmp2 r5
#define const_m1 r12
/* Additional internal variables for 64-bit aligned data. */
#define data1a r2
#define data1b r3
#define data2a r6
#define data2b r7
#define syndrome_a tmp1
#define syndrome_b tmp2
/* Additional internal variables for 32-bit aligned data. */
#define data1 r2
#define data2 r3
#define syndrome tmp2
/* Implementation of strcmp for ARMv7 when DSP instructions are
available. Use ldrd to support wider loads, provided the data
is sufficiently aligned. Use saturating arithmetic to optimize
the compares. */
/* Build Options:
STRCMP_NO_PRECHECK: Don't run a quick pre-check of the first
byte in the string. If comparing completely random strings
the pre-check will save time, since there is a very high
probability of a mismatch in the first character: we save
significant overhead if this is the common case. However,
if strings are likely to be identical (eg because we're
verifying a hit in a hash table), then this check is largely
redundant. */
.syntax unified
.thumb
// To avoid warning about deprecated instructions, add an explicit
// arch. The code generated is exactly the same.
.arch armv7-a
/* Macro to compute and return the result value for word-aligned
cases. */
.macro strcmp_epilogue_aligned synd d1 d2 restore_r6
#ifdef __ARM_BIG_ENDIAN
/* If data1 contains a zero byte, then syndrome will contain a 1 in
bit 7 of that byte. Otherwise, the highest set bit in the
syndrome will highlight the first different bit. It is therefore
sufficient to extract the eight bits starting with the syndrome
bit. */
clz tmp1, \synd
lsl r1, \d2, tmp1
.if \restore_r6
ldrd r6, r7, [sp, #8]
.endif
.cfi_restore 6
.cfi_restore 7
lsl \d1, \d1, tmp1
.cfi_remember_state
lsr result, \d1, #24
ldrd r4, r5, [sp], #16
.cfi_restore 4
.cfi_restore 5
sub result, result, r1, lsr #24
bx lr
#else
/* To use the big-endian trick we'd have to reverse all three words.
that's slower than this approach. */
rev \synd, \synd
clz tmp1, \synd
bic tmp1, tmp1, #7
lsr r1, \d2, tmp1
.cfi_remember_state
.if \restore_r6
ldrd r6, r7, [sp, #8]
.endif
.cfi_restore 6
.cfi_restore 7
lsr \d1, \d1, tmp1
and result, \d1, #255
and r1, r1, #255
ldrd r4, r5, [sp], #16
.cfi_restore 4
.cfi_restore 5
sub result, result, r1
bx lr
#endif
.endm
.text
.p2align 5
.Lstrcmp_start_addr:
#ifndef STRCMP_NO_PRECHECK
.Lfastpath_exit:
sub r0, r2, r3
bx lr
nop
#endif
ENTRY(strcmp_a15)
/* Use LDRD whenever possible. */
#ifndef STRCMP_NO_PRECHECK
ldrb r2, [src1]
ldrb r3, [src2]
cmp r2, #1
it cs
cmpcs r2, r3
bne .Lfastpath_exit
#endif
.cfi_sections .debug_frame
strd r4, r5, [sp, #-16]!
.cfi_def_cfa_offset 16
.cfi_offset 4, -16
.cfi_offset 5, -12
orr tmp1, src1, src2
strd r6, r7, [sp, #8]
.cfi_offset 6, -8
.cfi_offset 7, -4
mvn const_m1, #0
lsl r2, tmp1, #29
cbz r2, .Lloop_aligned8
/* The main thing to look out for when comparing large blocks is that
the loads do not cross a page boundary when loading past the index
of the byte with the first difference or the first string-terminator.
.Lnot_aligned:
eor tmp1, src1, src2
tst tmp1, #7
bne .Lmisaligned8
For example, if the strings are identical and the string-terminator
is at index k, byte by byte comparison will not load beyond address
s1+k and s2+k; word by word comparison may load up to 3 bytes beyond
k; double word - up to 7 bytes. If the load of these bytes crosses
a page boundary, it might cause a memory fault (if the page is not mapped)
that would not have happened in byte by byte comparison.
/* Deal with mutual misalignment by aligning downwards and then
masking off the unwanted loaded data to prevent a difference. */
and tmp1, src1, #7
bic src1, src1, #7
and tmp2, tmp1, #3
bic src2, src2, #7
lsl tmp2, tmp2, #3 /* Bytes -> bits. */
ldrd data1a, data1b, [src1], #16
tst tmp1, #4
ldrd data2a, data2b, [src2], #16
/* In thumb code we can't use MVN with a register shift, but
we do have ORN. */
S2HI tmp1, const_m1, tmp2
orn data1a, data1a, tmp1
orn data2a, data2a, tmp1
beq .Lstart_realigned8
orn data1b, data1b, tmp1
mov data1a, const_m1
orn data2b, data2b, tmp1
mov data2a, const_m1
b .Lstart_realigned8
If an address is (double) word aligned, then a load of a (double) word
from that address will not cross a page boundary.
Therefore, the algorithm below considers word and double-word alignment
of strings separately. */
/* Unwind the inner loop by a factor of 2, giving 16 bytes per
pass. */
.p2align 5,,12 /* Don't start in the tail bytes of a cache line. */
.p2align 2 /* Always word aligned. */
.Lloop_aligned8:
ldrd data1a, data1b, [src1], #16
ldrd data2a, data2b, [src2], #16
.Lstart_realigned8:
uadd8 syndrome_b, data1a, const_m1 /* Only want GE bits, */
eor syndrome_a, data1a, data2a
sel syndrome_a, syndrome_a, const_m1
cbnz syndrome_a, .Ldiff_in_a
uadd8 syndrome_b, data1b, const_m1 /* Only want GE bits. */
eor syndrome_b, data1b, data2b
sel syndrome_b, syndrome_b, const_m1
cbnz syndrome_b, .Ldiff_in_b
/* High-level description of the algorithm.
ldrd data1a, data1b, [src1, #-8]
ldrd data2a, data2b, [src2, #-8]
uadd8 syndrome_b, data1a, const_m1 /* Only want GE bits, */
eor syndrome_a, data1a, data2a
sel syndrome_a, syndrome_a, const_m1
uadd8 syndrome_b, data1b, const_m1 /* Only want GE bits. */
eor syndrome_b, data1b, data2b
sel syndrome_b, syndrome_b, const_m1
/* Can't use CBZ for backwards branch. */
orrs syndrome_b, syndrome_b, syndrome_a /* Only need if s_a == 0 */
beq .Lloop_aligned8
* The fast path: if both strings are double-word aligned,
use LDRD to load two words from each string in every loop iteration.
* If the strings have the same offset from a word boundary,
use LDRB to load and compare byte by byte until
the first string is aligned to a word boundary (at most 3 bytes).
This is optimized for quick return on short unaligned strings.
* If the strings have the same offset from a double-word boundary,
use LDRD to load two words from each string in every loop iteration, as in the fast path.
* If the strings do not have the same offset from a double-word boundary,
load a word from the second string before the loop to initialize the queue.
Use LDRD to load two words from every string in every loop iteration.
Inside the loop, load the second word from the second string only after comparing
the first word, using the queued value, to guarantee safety across page boundaries.
* If the strings do not have the same offset from a word boundary,
use LDR and a shift queue. Order of loads and comparisons matters,
similarly to the previous case.
.Ldiff_found:
cbnz syndrome_a, .Ldiff_in_a
* Use UADD8 and SEL to compare words, and use REV and CLZ to compute the return value.
* The only difference between ARM and Thumb modes is the use of CBZ instruction.
* The only difference between big and little endian is the use of REV in little endian
to compute the return value, instead of MOV.
*/
.Ldiff_in_b:
strcmp_epilogue_aligned syndrome_b, data1b, data2b 1
.macro m_cbz reg label
#ifdef __thumb2__
cbz \reg, \label
#else /* not defined __thumb2__ */
cmp \reg, #0
beq \label
#endif /* not defined __thumb2__ */
.endm /* m_cbz */
.Ldiff_in_a:
.cfi_restore_state
strcmp_epilogue_aligned syndrome_a, data1a, data2a 1
.macro m_cbnz reg label
#ifdef __thumb2__
cbnz \reg, \label
#else /* not defined __thumb2__ */
cmp \reg, #0
bne \label
#endif /* not defined __thumb2__ */
.endm /* m_cbnz */
.cfi_restore_state
.Lmisaligned8:
tst tmp1, #3
bne .Lmisaligned4
ands tmp1, src1, #3
bne .Lmutual_align4
.macro init
/* Macro to save temporary registers and prepare magic values. */
subs sp, sp, #16
.cfi_def_cfa_offset 16
strd r4, r5, [sp, #8]
.cfi_rel_offset r4, 0
.cfi_rel_offset r5, 4
strd r6, r7, [sp]
.cfi_rel_offset r6, 8
.cfi_rel_offset r7, 12
mvn r6, #0 /* all F */
mov r7, #0 /* all 0 */
.endm /* init */
/* Unrolled by a factor of 2, to reduce the number of post-increment
operations. */
.Lloop_aligned4:
ldr data1, [src1], #8
ldr data2, [src2], #8
.Lstart_realigned4:
uadd8 syndrome, data1, const_m1 /* Only need GE bits. */
eor syndrome, data1, data2
sel syndrome, syndrome, const_m1
cbnz syndrome, .Laligned4_done
ldr data1, [src1, #-4]
ldr data2, [src2, #-4]
uadd8 syndrome, data1, const_m1
eor syndrome, data1, data2
sel syndrome, syndrome, const_m1
cmp syndrome, #0
beq .Lloop_aligned4
.macro magic_compare_and_branch w1 w2 label
/* Macro to compare registers w1 and w2 and conditionally branch to label. */
cmp \w1, \w2 /* Are w1 and w2 the same? */
magic_find_zero_bytes \w1
it eq
cmpeq ip, #0 /* Is there a zero byte in w1? */
bne \label
.endm /* magic_compare_and_branch */
.Laligned4_done:
strcmp_epilogue_aligned syndrome, data1, data2, 0
.macro magic_find_zero_bytes w1
/* Macro to find all-zero bytes in w1, result is in ip. */
uadd8 ip, \w1, r6
sel ip, r7, r6
.endm /* magic_find_zero_bytes */
.Lmutual_align4:
.cfi_restore_state
/* Deal with mutual misalignment by aligning downwards and then
masking off the unwanted loaded data to prevent a difference. */
lsl tmp1, tmp1, #3 /* Bytes -> bits. */
bic src1, src1, #3
ldr data1, [src1], #8
bic src2, src2, #3
ldr data2, [src2], #8
.macro setup_return w1 w2
#ifdef __ARMEB__
mov r1, \w1
mov r2, \w2
#else /* not __ARMEB__ */
rev r1, \w1
rev r2, \w2
#endif /* not __ARMEB__ */
.endm /* setup_return */
/* In thumb code we can't use MVN with a register shift, but
we do have ORN. */
S2HI tmp1, const_m1, tmp1
orn data1, data1, tmp1
orn data2, data2, tmp1
b .Lstart_realigned4
pld [r0, #0]
pld [r1, #0]
.Lmisaligned4:
ands tmp1, src1, #3
beq .Lsrc1_aligned
sub src2, src2, tmp1
bic src1, src1, #3
lsls tmp1, tmp1, #31
ldr data1, [src1], #4
beq .Laligned_m2
bcs .Laligned_m1
/* Are both strings double-word aligned? */
orr ip, r0, r1
tst ip, #7
bne .L_do_align
#ifdef STRCMP_NO_PRECHECK
ldrb data2, [src2, #1]
uxtb tmp1, data1, ror #BYTE1_OFFSET
subs tmp1, tmp1, data2
bne .Lmisaligned_exit
cbz data2, .Lmisaligned_exit
/* Fast path. */
init
.Laligned_m2:
ldrb data2, [src2, #2]
uxtb tmp1, data1, ror #BYTE2_OFFSET
subs tmp1, tmp1, data2
bne .Lmisaligned_exit
cbz data2, .Lmisaligned_exit
.L_doubleword_aligned:
.Laligned_m1:
ldrb data2, [src2, #3]
uxtb tmp1, data1, ror #BYTE3_OFFSET
subs tmp1, tmp1, data2
bne .Lmisaligned_exit
add src2, src2, #4
cbnz data2, .Lsrc1_aligned
#else /* STRCMP_NO_PRECHECK */
/* If we've done the pre-check, then we don't need to check the
first byte again here. */
ldrb data2, [src2, #2]
uxtb tmp1, data1, ror #BYTE2_OFFSET
subs tmp1, tmp1, data2
bne .Lmisaligned_exit
cbz data2, .Lmisaligned_exit
/* Get here when the strings to compare are double-word aligned. */
/* Compare two words in every iteration. */
.p2align 2
2:
pld [r0, #16]
pld [r1, #16]
.Laligned_m2:
ldrb data2, [src2, #3]
uxtb tmp1, data1, ror #BYTE3_OFFSET
subs tmp1, tmp1, data2
bne .Lmisaligned_exit
cbnz data2, .Laligned_m1
#endif
/* Load the next double-word from each string. */
ldrd r2, r3, [r0], #8
ldrd r4, r5, [r1], #8
.Lmisaligned_exit:
.cfi_remember_state
mov result, tmp1
ldr r4, [sp], #16
.cfi_restore 4
bx lr
magic_compare_and_branch w1=r2, w2=r4, label=.L_return_24
magic_compare_and_branch w1=r3, w2=r5, label=.L_return_35
b 2b
#ifndef STRCMP_NO_PRECHECK
.Laligned_m1:
add src2, src2, #4
#endif
.Lsrc1_aligned:
.cfi_restore_state
/* src1 is word aligned, but src2 has no common alignment
with it. */
ldr data1, [src1], #4
lsls tmp1, src2, #31 /* C=src2[1], Z=src2[0]. */
.L_do_align:
/* Is the first string word-aligned? */
ands ip, r0, #3
beq .L_word_aligned_r0
bic src2, src2, #3
ldr data2, [src2], #4
bhi .Loverlap1 /* C=1, Z=0 => src2[1:0] = 0b11. */
bcs .Loverlap2 /* C=1, Z=1 => src2[1:0] = 0b10. */
/* Fast compare byte by byte until the first string is word-aligned. */
/* The offset of r0 from a word boundary is in ip. Thus, the number of bytes
to read until the next word boundary is 4-ip. */
bic r0, r0, #3
ldr r2, [r0], #4
lsls ip, ip, #31
beq .L_byte2
bcs .L_byte3
/* (overlap3) C=0, Z=0 => src2[1:0] = 0b01. */
.Loverlap3:
bic tmp1, data1, #MSB
uadd8 syndrome, data1, const_m1
eors syndrome, tmp1, data2, S2LO #8
sel syndrome, syndrome, const_m1
bne 4f
cbnz syndrome, 5f
ldr data2, [src2], #4
eor tmp1, tmp1, data1
cmp tmp1, data2, S2HI #24
bne 6f
ldr data1, [src1], #4
b .Loverlap3
4:
S2LO data2, data2, #8
b .Lstrcmp_tail
.L_byte1:
ldrb ip, [r1], #1
uxtb r3, r2, ror #BYTE1_OFFSET
subs ip, r3, ip
bne .L_fast_return
m_cbz reg=r3, label=.L_fast_return
5:
bics syndrome, syndrome, #MSB
bne .Lstrcmp_done_equal
.L_byte2:
ldrb ip, [r1], #1
uxtb r3, r2, ror #BYTE2_OFFSET
subs ip, r3, ip
bne .L_fast_return
m_cbz reg=r3, label=.L_fast_return
/* We can only get here if the MSB of data1 contains 0, so
fast-path the exit. */
ldrb result, [src2]
.cfi_remember_state
ldrd r4, r5, [sp], #16
.cfi_restore 4
.cfi_restore 5
/* R6/7 Not used in this sequence. */
.cfi_restore 6
.cfi_restore 7
neg result, result
bx lr
.L_byte3:
ldrb ip, [r1], #1
uxtb r3, r2, ror #BYTE3_OFFSET
subs ip, r3, ip
bne .L_fast_return
m_cbnz reg=r3, label=.L_word_aligned_r0
6:
.cfi_restore_state
S2LO data1, data1, #24
and data2, data2, #LSB
b .Lstrcmp_tail
.L_fast_return:
mov r0, ip
bx lr
.p2align 5,,12 /* Ensure at least 3 instructions in cache line. */
.Loverlap2:
and tmp1, data1, const_m1, S2LO #16
uadd8 syndrome, data1, const_m1
eors syndrome, tmp1, data2, S2LO #16
sel syndrome, syndrome, const_m1
bne 4f
cbnz syndrome, 5f
ldr data2, [src2], #4
eor tmp1, tmp1, data1
cmp tmp1, data2, S2HI #16
bne 6f
ldr data1, [src1], #4
b .Loverlap2
4:
S2LO data2, data2, #16
b .Lstrcmp_tail
5:
ands syndrome, syndrome, const_m1, S2LO #16
bne .Lstrcmp_done_equal
.L_word_aligned_r0:
init
/* The first string is word-aligned. */
/* Is the second string word-aligned? */
ands ip, r1, #3
bne .L_strcmp_unaligned
ldrh data2, [src2]
S2LO data1, data1, #16
#ifdef __ARM_BIG_ENDIAN
lsl data2, data2, #16
#endif
b .Lstrcmp_tail
.L_word_aligned:
/* The strings are word-aligned. */
/* Is the first string double-word aligned? */
tst r0, #4
beq .L_doubleword_aligned_r0
6:
S2LO data1, data1, #16
and data2, data2, const_m1, S2LO #16
b .Lstrcmp_tail
/* If r0 is not double-word aligned yet, align it by loading
and comparing the next word from each string. */
ldr r2, [r0], #4
ldr r4, [r1], #4
magic_compare_and_branch w1=r2 w2=r4 label=.L_return_24
.p2align 5,,12 /* Ensure at least 3 instructions in cache line. */
.Loverlap1:
and tmp1, data1, #LSB
uadd8 syndrome, data1, const_m1
eors syndrome, tmp1, data2, S2LO #24
sel syndrome, syndrome, const_m1
bne 4f
cbnz syndrome, 5f
ldr data2, [src2], #4
eor tmp1, tmp1, data1
cmp tmp1, data2, S2HI #8
bne 6f
ldr data1, [src1], #4
b .Loverlap1
4:
S2LO data2, data2, #24
b .Lstrcmp_tail
5:
tst syndrome, #LSB
bne .Lstrcmp_done_equal
ldr data2, [src2]
6:
S2LO data1, data1, #8
bic data2, data2, #MSB
b .Lstrcmp_tail
.L_doubleword_aligned_r0:
/* Get here when r0 is double-word aligned. */
/* Is r1 doubleword_aligned? */
tst r1, #4
beq .L_doubleword_aligned
.Lstrcmp_done_equal:
mov result, #0
.cfi_remember_state
ldrd r4, r5, [sp], #16
.cfi_restore 4
.cfi_restore 5
/* R6/7 not used in this sequence. */
.cfi_restore 6
.cfi_restore 7
bx lr
/* Get here when the strings to compare are word-aligned,
r0 is double-word aligned, but r1 is not double-word aligned. */
/* Initialize the queue. */
ldr r5, [r1], #4
/* Compare two words in every iteration. */
.p2align 2
3:
pld [r0, #16]
pld [r1, #16]
/* Load the next double-word from each string and compare. */
ldrd r2, r3, [r0], #8
magic_compare_and_branch w1=r2 w2=r5 label=.L_return_25
ldrd r4, r5, [r1], #8
magic_compare_and_branch w1=r3 w2=r4 label=.L_return_34
b 3b
.macro miscmp_word offsetlo offsethi
/* Macro to compare misaligned strings. */
/* r0, r1 are word-aligned, and at least one of the strings
is not double-word aligned. */
/* Compare one word in every loop iteration. */
/* OFFSETLO is the original bit-offset of r1 from a word-boundary,
OFFSETHI is 32 - OFFSETLO (i.e., offset from the next word). */
/* Initialize the shift queue. */
ldr r5, [r1], #4
/* Compare one word from each string in every loop iteration. */
.p2align 2
7:
ldr r3, [r0], #4
S2LOMEM r5, r5, #\offsetlo
magic_find_zero_bytes w1=r3
cmp r7, ip, S2HIMEM #\offsetlo
and r2, r3, r6, S2LOMEM #\offsetlo
it eq
cmpeq r2, r5
bne .L_return_25
ldr r5, [r1], #4
cmp ip, #0
eor r3, r2, r3
S2HIMEM r2, r5, #\offsethi
it eq
cmpeq r3, r2
bne .L_return_32
b 7b
.endm /* miscmp_word */
.L_strcmp_unaligned:
/* r0 is word-aligned, r1 is at offset ip from a word. */
/* Align r1 to the (previous) word-boundary. */
bic r1, r1, #3
/* Unaligned comparison word by word using LDRs. */
cmp ip, #2
beq .L_miscmp_word_16 /* If ip == 2. */
bge .L_miscmp_word_24 /* If ip == 3. */
miscmp_word offsetlo=8 offsethi=24 /* If ip == 1. */
.L_miscmp_word_16: miscmp_word offsetlo=16 offsethi=16
.L_miscmp_word_24: miscmp_word offsetlo=24 offsethi=8
.L_return_32:
setup_return w1=r3, w2=r2
b .L_do_return
.L_return_34:
setup_return w1=r3, w2=r4
b .L_do_return
.L_return_25:
setup_return w1=r2, w2=r5
b .L_do_return
.L_return_35:
setup_return w1=r3, w2=r5
b .L_do_return
.L_return_24:
setup_return w1=r2, w2=r4
.L_do_return:
#ifdef __ARMEB__
mov r0, ip
#else /* not __ARMEB__ */
rev r0, ip
#endif /* not __ARMEB__ */
/* Restore temporaries early, before computing the return value. */
ldrd r6, r7, [sp]
ldrd r4, r5, [sp, #8]
adds sp, sp, #16
.cfi_def_cfa_offset 0
.cfi_restore r4
.cfi_restore r5
.cfi_restore r6
.cfi_restore r7
/* There is a zero or a different byte between r1 and r2. */
/* r0 contains a mask of all-zero bytes in r1. */
/* Using r0 and not ip here because cbz requires low register. */
m_cbz reg=r0, label=.L_compute_return_value
clz r0, r0
/* r0 contains the number of bits on the left of the first all-zero byte in r1. */
rsb r0, r0, #24
/* Here, r0 contains the number of bits on the right of the first all-zero byte in r1. */
lsr r1, r1, r0
lsr r2, r2, r0
.L_compute_return_value:
movs r0, #1
cmp r1, r2
/* The return value is computed as follows.
If r1>r2 then (C==1 and Z==0) and LS doesn't hold and r0 is #1 at return.
If r1<r2 then (C==0 and Z==0) and we execute SBC with carry_in=0,
which means r0:=r0-r0-1 and r0 is #-1 at return.
If r1=r2 then (C==1 and Z==1) and we execute SBC with carry_in=1,
which means r0:=r0-r0 and r0 is #0 at return.
(C==0 and Z==1) cannot happen because the carry bit is "not borrow". */
it ls
sbcls r0, r0, r0
bx lr
.Lstrcmp_tail:
.cfi_restore_state
#ifndef __ARM_BIG_ENDIAN
rev data1, data1
rev data2, data2
/* Now everything looks big-endian... */
#endif
uadd8 tmp1, data1, const_m1
eor tmp1, data1, data2
sel syndrome, tmp1, const_m1
clz tmp1, syndrome
lsl data1, data1, tmp1
lsl data2, data2, tmp1
lsr result, data1, #24
ldrd r4, r5, [sp], #16
.cfi_restore 4
.cfi_restore 5
/* R6/7 not used in this sequence. */
.cfi_restore 6
.cfi_restore 7
sub result, result, data2, lsr #24
bx lr
END(strcmp_a15)

551
libc/arch-arm/cortex-a9/bionic/strcmp.S
View file

@ -1,551 +0,0 @@
/*
* Copyright (c) 2013 ARM Ltd
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. The name of the company may not be used to endorse or promote
* products derived from this software without specific prior written
* permission.
*
* THIS SOFTWARE IS PROVIDED BY ARM LTD ``AS IS'' AND ANY EXPRESS OR IMPLIED
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL ARM LTD BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
* TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include <private/bionic_asm.h>
#ifdef __ARMEB__
#define S2LOMEM lsl
#define S2LOMEMEQ lsleq
#define S2HIMEM lsr
#define MSB 0x000000ff
#define LSB 0xff000000
#define BYTE0_OFFSET 24
#define BYTE1_OFFSET 16
#define BYTE2_OFFSET 8
#define BYTE3_OFFSET 0
#else /* not __ARMEB__ */
#define S2LOMEM lsr
#define S2LOMEMEQ lsreq
#define S2HIMEM lsl
#define BYTE0_OFFSET 0
#define BYTE1_OFFSET 8
#define BYTE2_OFFSET 16
#define BYTE3_OFFSET 24
#define MSB 0xff000000
#define LSB 0x000000ff
#endif /* not __ARMEB__ */
.syntax unified
// To avoid warning about deprecated instructions, add an explicit
// arch. The code generated is exactly the same.
.arch armv7-a
#if defined (__thumb__)
.thumb
.thumb_func
#endif
ENTRY(strcmp_a9)
/* Use LDRD whenever possible. */
/* The main thing to look out for when comparing large blocks is that
the loads do not cross a page boundary when loading past the index
of the byte with the first difference or the first string-terminator.
For example, if the strings are identical and the string-terminator
is at index k, byte by byte comparison will not load beyond address
s1+k and s2+k; word by word comparison may load up to 3 bytes beyond
k; double word - up to 7 bytes. If the load of these bytes crosses
a page boundary, it might cause a memory fault (if the page is not mapped)
that would not have happened in byte by byte comparison.
If an address is (double) word aligned, then a load of a (double) word
from that address will not cross a page boundary.
Therefore, the algorithm below considers word and double-word alignment
of strings separately. */
/* High-level description of the algorithm.
* The fast path: if both strings are double-word aligned,
use LDRD to load two words from each string in every loop iteration.
* If the strings have the same offset from a word boundary,
use LDRB to load and compare byte by byte until
the first string is aligned to a word boundary (at most 3 bytes).
This is optimized for quick return on short unaligned strings.
* If the strings have the same offset from a double-word boundary,
use LDRD to load two words from each string in every loop iteration, as in the fast path.
* If the strings do not have the same offset from a double-word boundary,
load a word from the second string before the loop to initialize the queue.
Use LDRD to load two words from every string in every loop iteration.
Inside the loop, load the second word from the second string only after comparing
the first word, using the queued value, to guarantee safety across page boundaries.
* If the strings do not have the same offset from a word boundary,
use LDR and a shift queue. Order of loads and comparisons matters,
similarly to the previous case.
* Use UADD8 and SEL to compare words, and use REV and CLZ to compute the return value.
* The only difference between ARM and Thumb modes is the use of CBZ instruction.
* The only difference between big and little endian is the use of REV in little endian
to compute the return value, instead of MOV.
*/
.macro m_cbz reg label
#ifdef __thumb2__
cbz \reg, \label
#else /* not defined __thumb2__ */
cmp \reg, #0
beq \label
#endif /* not defined __thumb2__ */
.endm /* m_cbz */
.macro m_cbnz reg label
#ifdef __thumb2__
cbnz \reg, \label
#else /* not defined __thumb2__ */
cmp \reg, #0
bne \label
#endif /* not defined __thumb2__ */
.endm /* m_cbnz */
.macro init
/* Macro to save temporary registers and prepare magic values. */
subs sp, sp, #16
.cfi_def_cfa_offset 16
strd r4, r5, [sp, #8]
.cfi_rel_offset r4, 0
.cfi_rel_offset r5, 4
strd r6, r7, [sp]
.cfi_rel_offset r6, 8
.cfi_rel_offset r7, 12
mvn r6, #0 /* all F */
mov r7, #0 /* all 0 */
.endm /* init */
.macro magic_compare_and_branch w1 w2 label
/* Macro to compare registers w1 and w2 and conditionally branch to label. */
cmp \w1, \w2 /* Are w1 and w2 the same? */
magic_find_zero_bytes \w1
it eq
cmpeq ip, #0 /* Is there a zero byte in w1? */
bne \label
.endm /* magic_compare_and_branch */
.macro magic_find_zero_bytes w1
/* Macro to find all-zero bytes in w1, result is in ip. */
uadd8 ip, \w1, r6
sel ip, r7, r6
.endm /* magic_find_zero_bytes */
.macro setup_return w1 w2
#ifdef __ARMEB__
mov r1, \w1
mov r2, \w2
#else /* not __ARMEB__ */
rev r1, \w1
rev r2, \w2
#endif /* not __ARMEB__ */
.endm /* setup_return */
pld [r0, #0]
pld [r1, #0]
/* Are both strings double-word aligned? */
orr ip, r0, r1
tst ip, #7
bne .L_do_align
/* Fast path. */
init
.L_doubleword_aligned:
/* Get here when the strings to compare are double-word aligned. */
/* Compare two words in every iteration. */
.p2align 2
2:
pld [r0, #16]
pld [r1, #16]
/* Load the next double-word from each string. */
ldrd r2, r3, [r0], #8
ldrd r4, r5, [r1], #8
magic_compare_and_branch w1=r2, w2=r4, label=.L_return_24
magic_compare_and_branch w1=r3, w2=r5, label=.L_return_35
b 2b
.L_do_align:
/* Is the first string word-aligned? */
ands ip, r0, #3
beq .L_word_aligned_r0
/* Fast compare byte by byte until the first string is word-aligned. */
/* The offset of r0 from a word boundary is in ip. Thus, the number of bytes
to read until the next word boundary is 4-ip. */
bic r0, r0, #3
ldr r2, [r0], #4
lsls ip, ip, #31
beq .L_byte2
bcs .L_byte3
.L_byte1:
ldrb ip, [r1], #1
uxtb r3, r2, ror #BYTE1_OFFSET
subs ip, r3, ip
bne .L_fast_return
m_cbz reg=r3, label=.L_fast_return
.L_byte2:
ldrb ip, [r1], #1
uxtb r3, r2, ror #BYTE2_OFFSET
subs ip, r3, ip
bne .L_fast_return
m_cbz reg=r3, label=.L_fast_return
.L_byte3:
ldrb ip, [r1], #1
uxtb r3, r2, ror #BYTE3_OFFSET
subs ip, r3, ip
bne .L_fast_return
m_cbnz reg=r3, label=.L_word_aligned_r0
.L_fast_return:
mov r0, ip
bx lr
.L_word_aligned_r0:
init
/* The first string is word-aligned. */
/* Is the second string word-aligned? */
ands ip, r1, #3
bne .L_strcmp_unaligned
.L_word_aligned:
/* The strings are word-aligned. */
/* Is the first string double-word aligned? */
tst r0, #4
beq .L_doubleword_aligned_r0
/* If r0 is not double-word aligned yet, align it by loading
and comparing the next word from each string. */
ldr r2, [r0], #4
ldr r4, [r1], #4
magic_compare_and_branch w1=r2 w2=r4 label=.L_return_24
.L_doubleword_aligned_r0:
/* Get here when r0 is double-word aligned. */
/* Is r1 doubleword_aligned? */
tst r1, #4
beq .L_doubleword_aligned
/* Get here when the strings to compare are word-aligned,
r0 is double-word aligned, but r1 is not double-word aligned. */
/* Initialize the queue. */
ldr r5, [r1], #4
/* Compare two words in every iteration. */
.p2align 2
3:
pld [r0, #16]
pld [r1, #16]
/* Load the next double-word from each string and compare. */
ldrd r2, r3, [r0], #8
magic_compare_and_branch w1=r2 w2=r5 label=.L_return_25
ldrd r4, r5, [r1], #8
magic_compare_and_branch w1=r3 w2=r4 label=.L_return_34
b 3b
.macro miscmp_word offsetlo offsethi
/* Macro to compare misaligned strings. */
/* r0, r1 are word-aligned, and at least one of the strings
is not double-word aligned. */
/* Compare one word in every loop iteration. */
/* OFFSETLO is the original bit-offset of r1 from a word-boundary,
OFFSETHI is 32 - OFFSETLO (i.e., offset from the next word). */
/* Initialize the shift queue. */
ldr r5, [r1], #4
/* Compare one word from each string in every loop iteration. */
.p2align 2
7:
ldr r3, [r0], #4
S2LOMEM r5, r5, #\offsetlo
magic_find_zero_bytes w1=r3
cmp r7, ip, S2HIMEM #\offsetlo
and r2, r3, r6, S2LOMEM #\offsetlo
it eq
cmpeq r2, r5
bne .L_return_25
ldr r5, [r1], #4
cmp ip, #0
eor r3, r2, r3
S2HIMEM r2, r5, #\offsethi
it eq
cmpeq r3, r2
bne .L_return_32
b 7b
.endm /* miscmp_word */
.L_return_32:
setup_return w1=r3, w2=r2
b .L_do_return
.L_return_34:
setup_return w1=r3, w2=r4
b .L_do_return
.L_return_25:
setup_return w1=r2, w2=r5
b .L_do_return
.L_return_35:
setup_return w1=r3, w2=r5
b .L_do_return
.L_return_24:
setup_return w1=r2, w2=r4
.L_do_return:
#ifdef __ARMEB__
mov r0, ip
#else /* not __ARMEB__ */
rev r0, ip
#endif /* not __ARMEB__ */
/* Restore temporaries early, before computing the return value. */
ldrd r6, r7, [sp]
ldrd r4, r5, [sp, #8]
adds sp, sp, #16
.cfi_def_cfa_offset 0
.cfi_restore r4
.cfi_restore r5
.cfi_restore r6
.cfi_restore r7
/* There is a zero or a different byte between r1 and r2. */
/* r0 contains a mask of all-zero bytes in r1. */
/* Using r0 and not ip here because cbz requires low register. */
m_cbz reg=r0, label=.L_compute_return_value
clz r0, r0
/* r0 contains the number of bits on the left of the first all-zero byte in r1. */
rsb r0, r0, #24
/* Here, r0 contains the number of bits on the right of the first all-zero byte in r1. */
lsr r1, r1, r0
lsr r2, r2, r0
.L_compute_return_value:
movs r0, #1
cmp r1, r2
/* The return value is computed as follows.
If r1>r2 then (C==1 and Z==0) and LS doesn't hold and r0 is #1 at return.
If r1<r2 then (C==0 and Z==0) and we execute SBC with carry_in=0,
which means r0:=r0-r0-1 and r0 is #-1 at return.
If r1=r2 then (C==1 and Z==1) and we execute SBC with carry_in=1,
which means r0:=r0-r0 and r0 is #0 at return.
(C==0 and Z==1) cannot happen because the carry bit is "not borrow". */
it ls
sbcls r0, r0, r0
bx lr
/* The code from the previous version of strcmp.S handles all of the
* cases where the first string and seconds string cannot both be
* aligned to a word boundary faster than the new algorithm. See
* bionic/libc/arch-arm/cortex-a15/bionic/strcmp.S for the unedited
* version of the code.
*/
.L_strcmp_unaligned:
wp1 .req r0
wp2 .req r1
b1 .req r2
w1 .req r4
w2 .req r5
t1 .req ip
@ r3 is scratch
2:
mov b1, #1
orr b1, b1, b1, lsl #8
orr b1, b1, b1, lsl #16
and t1, wp2, #3
bic wp2, wp2, #3
ldr w1, [wp1], #4
ldr w2, [wp2], #4
cmp t1, #2
beq 2f
bhi 3f
/* Critical inner Loop: Block with 3 bytes initial overlap */
.p2align 2
1:
bic t1, w1, #MSB
cmp t1, w2, S2LOMEM #8
sub r3, w1, b1
bic r3, r3, w1
bne 4f
ands r3, r3, b1, lsl #7
it eq
ldreq w2, [wp2], #4
bne 5f
eor t1, t1, w1
cmp t1, w2, S2HIMEM #24
bne 6f
ldr w1, [wp1], #4
b 1b
4:
S2LOMEM w2, w2, #8
b 8f
5:
#ifdef __ARMEB__
/* The syndrome value may contain false ones if the string ends
* with the bytes 0x01 0x00
*/
tst w1, #0xff000000
itt ne
tstne w1, #0x00ff0000
tstne w1, #0x0000ff00
beq 7f
#else
bics r3, r3, #0xff000000
bne 7f
#endif
ldrb w2, [wp2]
S2LOMEM t1, w1, #24
#ifdef __ARMEB__
lsl w2, w2, #24
#endif
b 8f
6:
S2LOMEM t1, w1, #24
and w2, w2, #LSB
b 8f
/* Critical inner Loop: Block with 2 bytes initial overlap */
.p2align 2
2:
S2HIMEM t1, w1, #16
sub r3, w1, b1
S2LOMEM t1, t1, #16
bic r3, r3, w1
cmp t1, w2, S2LOMEM #16
bne 4f
ands r3, r3, b1, lsl #7
it eq
ldreq w2, [wp2], #4
bne 5f
eor t1, t1, w1
cmp t1, w2, S2HIMEM #16
bne 6f
ldr w1, [wp1], #4
b 2b
5:
#ifdef __ARMEB__
/* The syndrome value may contain false ones if the string ends
* with the bytes 0x01 0x00
*/
tst w1, #0xff000000
it ne
tstne w1, #0x00ff0000
beq 7f
#else
lsls r3, r3, #16
bne 7f
#endif
ldrh w2, [wp2]
S2LOMEM t1, w1, #16
#ifdef __ARMEB__
lsl w2, w2, #16
#endif
b 8f
6:
S2HIMEM w2, w2, #16
S2LOMEM t1, w1, #16
4:
S2LOMEM w2, w2, #16
b 8f
/* Critical inner Loop: Block with 1 byte initial overlap */
.p2align 2
3:
and t1, w1, #LSB
cmp t1, w2, S2LOMEM #24
sub r3, w1, b1
bic r3, r3, w1
bne 4f
ands r3, r3, b1, lsl #7
it eq
ldreq w2, [wp2], #4
bne 5f
eor t1, t1, w1
cmp t1, w2, S2HIMEM #8
bne 6f
ldr w1, [wp1], #4
b 3b
4:
S2LOMEM w2, w2, #24
b 8f
5:
/* The syndrome value may contain false ones if the string ends
* with the bytes 0x01 0x00
*/
tst w1, #LSB
beq 7f
ldr w2, [wp2], #4
6:
S2LOMEM t1, w1, #8
bic w2, w2, #MSB
b 8f
7:
mov r0, #0
/* Restore registers and stack. */
ldrd r6, r7, [sp]
ldrd r4, r5, [sp, #8]
adds sp, sp, #16
.cfi_def_cfa_offset 0
.cfi_restore r4
.cfi_restore r5
.cfi_restore r6
.cfi_restore r7
bx lr
8:
and r2, t1, #LSB
and r0, w2, #LSB
cmp r0, #1
it cs
cmpcs r0, r2
itt eq
S2LOMEMEQ t1, t1, #8
S2LOMEMEQ w2, w2, #8
beq 8b
sub r0, r2, r0
/* Restore registers and stack. */
ldrd r6, r7, [sp]
ldrd r4, r5, [sp, #8]
adds sp, sp, #16
bx lr
END(strcmp_a9)

11
libc/arch-arm/dynamic_function_dispatch.cpp
View file

@ -288,16 +288,7 @@ DEFINE_IFUNC(__strcat_chk) {
typedef int strcmp_func(const char* __lhs, const char* __rhs);
DEFINE_IFUNC(strcmp) {
switch(get_cpu_variant()) {
case kCortexA9:
RETURN_FUNC(strcmp_func, strcmp_a9);
case kCortexA55:
case kKrait:
case kKryo:
RETURN_FUNC(strcmp_func, strcmp_krait);
default:
RETURN_FUNC(strcmp_func, strcmp_a15);
}
RETURN_FUNC(strcmp_func, strcmp_a15);
}
typedef size_t strlen_func(const char* __s);

489
libc/arch-arm/krait/bionic/strcmp.S
View file

@ -1,489 +0,0 @@
/*
* Copyright (c) 2013 ARM Ltd
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. The name of the company may not be used to endorse or promote
* products derived from this software without specific prior written
* permission.
*
* THIS SOFTWARE IS PROVIDED BY ARM LTD ``AS IS'' AND ANY EXPRESS OR IMPLIED
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL ARM LTD BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
* TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include <private/bionic_asm.h>
#ifdef __ARMEB__
#define S2LOMEM lsl
#define S2LOMEMEQ lsleq
#define S2HIMEM lsr
#define MSB 0x000000ff
#define LSB 0xff000000
#define BYTE0_OFFSET 24
#define BYTE1_OFFSET 16
#define BYTE2_OFFSET 8
#define BYTE3_OFFSET 0
#else /* not __ARMEB__ */
#define S2LOMEM lsr
#define S2LOMEMEQ lsreq
#define S2HIMEM lsl
#define BYTE0_OFFSET 0
#define BYTE1_OFFSET 8
#define BYTE2_OFFSET 16
#define BYTE3_OFFSET 24
#define MSB 0xff000000
#define LSB 0x000000ff
#endif /* not __ARMEB__ */
.syntax unified
// To avoid warning about deprecated instructions, add an explicit
// arch. The code generated is exactly the same.
.arch armv7-a
#if defined (__thumb__)
.thumb
.thumb_func
#endif
ENTRY(strcmp_krait)
/* Use LDRD whenever possible. */
/* The main thing to look out for when comparing large blocks is that
the loads do not cross a page boundary when loading past the index
of the byte with the first difference or the first string-terminator.
For example, if the strings are identical and the string-terminator
is at index k, byte by byte comparison will not load beyond address
s1+k and s2+k; word by word comparison may load up to 3 bytes beyond
k; double word - up to 7 bytes. If the load of these bytes crosses
a page boundary, it might cause a memory fault (if the page is not mapped)
that would not have happened in byte by byte comparison.
If an address is (double) word aligned, then a load of a (double) word
from that address will not cross a page boundary.
Therefore, the algorithm below considers word and double-word alignment
of strings separately. */
/* High-level description of the algorithm.
* The fast path: if both strings are double-word aligned,
use LDRD to load two words from each string in every loop iteration.
* If the strings have the same offset from a word boundary,
use LDRB to load and compare byte by byte until
the first string is aligned to a word boundary (at most 3 bytes).
This is optimized for quick return on short unaligned strings.
* If the strings have the same offset from a double-word boundary,
use LDRD to load two words from each string in every loop iteration, as in the fast path.
* If the strings do not have the same offset from a double-word boundary,
load a word from the second string before the loop to initialize the queue.
Use LDRD to load two words from every string in every loop iteration.
Inside the loop, load the second word from the second string only after comparing
the first word, using the queued value, to guarantee safety across page boundaries.
* If the strings do not have the same offset from a word boundary,
use LDR and a shift queue. Order of loads and comparisons matters,
similarly to the previous case.
* Use UADD8 and SEL to compare words, and use REV and CLZ to compute the return value.
* The only difference between ARM and Thumb modes is the use of CBZ instruction.
* The only difference between big and little endian is the use of REV in little endian
to compute the return value, instead of MOV.
*/
.macro m_cbz reg label
#ifdef __thumb2__
cbz \reg, \label
#else /* not defined __thumb2__ */
cmp \reg, #0
beq \label
#endif /* not defined __thumb2__ */
.endm /* m_cbz */
.macro m_cbnz reg label
#ifdef __thumb2__
cbnz \reg, \label
#else /* not defined __thumb2__ */
cmp \reg, #0
bne \label
#endif /* not defined __thumb2__ */
.endm /* m_cbnz */
.macro init
/* Macro to save temporary registers and prepare magic values. */
subs sp, sp, #16
.cfi_def_cfa_offset 16
strd r4, r5, [sp, #8]
.cfi_rel_offset r4, 0
.cfi_rel_offset r5, 4
strd r6, r7, [sp]
.cfi_rel_offset r6, 8
.cfi_rel_offset r7, 12
mvn r6, #0 /* all F */
mov r7, #0 /* all 0 */
.endm /* init */
.macro magic_compare_and_branch w1 w2 label
/* Macro to compare registers w1 and w2 and conditionally branch to label. */
cmp \w1, \w2 /* Are w1 and w2 the same? */
magic_find_zero_bytes \w1
it eq
cmpeq ip, #0 /* Is there a zero byte in w1? */
bne \label
.endm /* magic_compare_and_branch */
.macro magic_find_zero_bytes w1
/* Macro to find all-zero bytes in w1, result is in ip. */
uadd8 ip, \w1, r6
sel ip, r7, r6
.endm /* magic_find_zero_bytes */
.macro setup_return w1 w2
#ifdef __ARMEB__
mov r1, \w1
mov r2, \w2
#else /* not __ARMEB__ */
rev r1, \w1
rev r2, \w2
#endif /* not __ARMEB__ */
.endm /* setup_return */
pld [r0, #0]
pld [r1, #0]
/* Are both strings double-word aligned? */
orr ip, r0, r1
tst ip, #7
bne .L_do_align
/* Fast path. */
init
.L_doubleword_aligned:
/* Get here when the strings to compare are double-word aligned. */
/* Compare two words in every iteration. */
.p2align 2
2:
pld [r0, #16]
pld [r1, #16]
/* Load the next double-word from each string. */
ldrd r2, r3, [r0], #8
ldrd r4, r5, [r1], #8
magic_compare_and_branch w1=r2, w2=r4, label=.L_return_24
magic_compare_and_branch w1=r3, w2=r5, label=.L_return_35
b 2b
.L_do_align:
/* Is the first string word-aligned? */
ands ip, r0, #3
beq .L_word_aligned_r0
/* Fast compare byte by byte until the first string is word-aligned. */
/* The offset of r0 from a word boundary is in ip. Thus, the number of bytes
to read until the next word boundary is 4-ip. */
bic r0, r0, #3
ldr r2, [r0], #4
lsls ip, ip, #31
beq .L_byte2
bcs .L_byte3
.L_byte1:
ldrb ip, [r1], #1
uxtb r3, r2, ror #BYTE1_OFFSET
subs ip, r3, ip
bne .L_fast_return
m_cbz reg=r3, label=.L_fast_return
.L_byte2:
ldrb ip, [r1], #1
uxtb r3, r2, ror #BYTE2_OFFSET
subs ip, r3, ip
bne .L_fast_return
m_cbz reg=r3, label=.L_fast_return
.L_byte3:
ldrb ip, [r1], #1
uxtb r3, r2, ror #BYTE3_OFFSET
subs ip, r3, ip
bne .L_fast_return
m_cbnz reg=r3, label=.L_word_aligned_r0
.L_fast_return:
mov r0, ip
bx lr
.L_word_aligned_r0:
init
/* The first string is word-aligned. */
/* Is the second string word-aligned? */
ands ip, r1, #3
bne .L_strcmp_unaligned
.L_word_aligned:
/* The strings are word-aligned. */
/* Is the first string double-word aligned? */
tst r0, #4
beq .L_doubleword_aligned_r0
/* If r0 is not double-word aligned yet, align it by loading
and comparing the next word from each string. */
ldr r2, [r0], #4
ldr r4, [r1], #4
magic_compare_and_branch w1=r2 w2=r4 label=.L_return_24
.L_doubleword_aligned_r0:
/* Get here when r0 is double-word aligned. */
/* Is r1 doubleword_aligned? */
tst r1, #4
beq .L_doubleword_aligned
/* Get here when the strings to compare are word-aligned,
r0 is double-word aligned, but r1 is not double-word aligned. */
/* Initialize the queue. */
ldr r5, [r1], #4
/* Compare two words in every iteration. */
.p2align 2
3:
pld [r0, #16]
pld [r1, #16]
/* Load the next double-word from each string and compare. */
ldrd r2, r3, [r0], #8
magic_compare_and_branch w1=r2 w2=r5 label=.L_return_25
ldrd r4, r5, [r1], #8
magic_compare_and_branch w1=r3 w2=r4 label=.L_return_34
b 3b
.macro miscmp_word offsetlo offsethi
/* Macro to compare misaligned strings. */
/* r0, r1 are word-aligned, and at least one of the strings
is not double-word aligned. */
/* Compare one word in every loop iteration. */
/* OFFSETLO is the original bit-offset of r1 from a word-boundary,
OFFSETHI is 32 - OFFSETLO (i.e., offset from the next word). */
/* Initialize the shift queue. */
ldr r5, [r1], #4
/* Compare one word from each string in every loop iteration. */
.p2align 2
7:
ldr r3, [r0], #4
S2LOMEM r5, r5, #\offsetlo
magic_find_zero_bytes w1=r3
cmp r7, ip, S2HIMEM #\offsetlo
and r2, r3, r6, S2LOMEM #\offsetlo
it eq
cmpeq r2, r5
bne .L_return_25
ldr r5, [r1], #4
cmp ip, #0
eor r3, r2, r3
S2HIMEM r2, r5, #\offsethi
it eq
cmpeq r3, r2
bne .L_return_32
b 7b
.endm /* miscmp_word */
.L_strcmp_unaligned:
/* r0 is word-aligned, r1 is at offset ip from a word. */
/* Align r1 to the (previous) word-boundary. */
bic r1, r1, #3
/* Unaligned comparison word by word using LDRs. */
cmp ip, #2
beq .L_miscmp_word_16 /* If ip == 2. */
bge .L_miscmp_word_24 /* If ip == 3. */
miscmp_word offsetlo=8 offsethi=24 /* If ip == 1. */
.L_miscmp_word_24: miscmp_word offsetlo=24 offsethi=8
.L_return_32:
setup_return w1=r3, w2=r2
b .L_do_return
.L_return_34:
setup_return w1=r3, w2=r4
b .L_do_return
.L_return_25:
setup_return w1=r2, w2=r5
b .L_do_return
.L_return_35:
setup_return w1=r3, w2=r5
b .L_do_return
.L_return_24:
setup_return w1=r2, w2=r4
.L_do_return:
#ifdef __ARMEB__
mov r0, ip
#else /* not __ARMEB__ */
rev r0, ip
#endif /* not __ARMEB__ */
/* Restore temporaries early, before computing the return value. */
ldrd r6, r7, [sp]
ldrd r4, r5, [sp, #8]
adds sp, sp, #16
.cfi_def_cfa_offset 0
.cfi_restore r4
.cfi_restore r5
.cfi_restore r6
.cfi_restore r7
/* There is a zero or a different byte between r1 and r2. */
/* r0 contains a mask of all-zero bytes in r1. */
/* Using r0 and not ip here because cbz requires low register. */
m_cbz reg=r0, label=.L_compute_return_value
clz r0, r0
/* r0 contains the number of bits on the left of the first all-zero byte in r1. */
rsb r0, r0, #24
/* Here, r0 contains the number of bits on the right of the first all-zero byte in r1. */
lsr r1, r1, r0
lsr r2, r2, r0
.L_compute_return_value:
movs r0, #1
cmp r1, r2
/* The return value is computed as follows.
If r1>r2 then (C==1 and Z==0) and LS doesn't hold and r0 is #1 at return.
If r1<r2 then (C==0 and Z==0) and we execute SBC with carry_in=0,
which means r0:=r0-r0-1 and r0 is #-1 at return.
If r1=r2 then (C==1 and Z==1) and we execute SBC with carry_in=1,
which means r0:=r0-r0 and r0 is #0 at return.
(C==0 and Z==1) cannot happen because the carry bit is "not borrow". */
it ls
sbcls r0, r0, r0
bx lr
/* The code from the previous version of strcmp.S handles this
* particular case (the second string is 2 bytes off a word alignment)
* faster than any current version. In this very specific case, use the
* previous version. See bionic/libc/arch-arm/cortex-a15/bionic/strcmp.S
* for the unedited version of this code.
*/
.L_miscmp_word_16:
wp1 .req r0
wp2 .req r1
b1 .req r2
w1 .req r4
w2 .req r5
t1 .req ip
@ r3 is scratch
/* At this point, wp1 (r0) has already been word-aligned. */
2:
mov b1, #1
orr b1, b1, b1, lsl #8
orr b1, b1, b1, lsl #16
and t1, wp2, #3
bic wp2, wp2, #3
ldr w1, [wp1], #4
ldr w2, [wp2], #4
/* Critical inner Loop: Block with 2 bytes initial overlap */
.p2align 2
2:
S2HIMEM t1, w1, #16
sub r3, w1, b1
S2LOMEM t1, t1, #16
bic r3, r3, w1
cmp t1, w2, S2LOMEM #16
bne 4f
ands r3, r3, b1, lsl #7
it eq
ldreq w2, [wp2], #4
bne 5f
eor t1, t1, w1
cmp t1, w2, S2HIMEM #16
bne 6f
ldr w1, [wp1], #4
b 2b
5:
#ifdef __ARMEB__
/* The syndrome value may contain false ones if the string ends
* with the bytes 0x01 0x00
*/
tst w1, #0xff000000
it ne
tstne w1, #0x00ff0000
beq 7f
#else
lsls r3, r3, #16
bne 7f
#endif
ldrh w2, [wp2]
S2LOMEM t1, w1, #16
#ifdef __ARMEB__
lsl w2, w2, #16
#endif
b 8f
6:
S2HIMEM w2, w2, #16
S2LOMEM t1, w1, #16
4:
S2LOMEM w2, w2, #16
b 8f
7:
mov r0, #0
/* Restore registers and stack. */
ldrd r6, r7, [sp]
ldrd r4, r5, [sp, #8]
adds sp, sp, #16
.cfi_def_cfa_offset 0
.cfi_restore r4
.cfi_restore r5
.cfi_restore r6
.cfi_restore r7
bx lr
8:
and r2, t1, #LSB
and r0, w2, #LSB
cmp r0, #1
it cs
cmpcs r0, r2
itt eq
S2LOMEMEQ t1, t1, #8
S2LOMEMEQ w2, w2, #8
beq 8b
sub r0, r2, r0
/* Restore registers and stack. */
ldrd r6, r7, [sp]
ldrd r4, r5, [sp, #8]
adds sp, sp, #16
.cfi_def_cfa_offset 0
.cfi_restore r4
.cfi_restore r5
.cfi_restore r6
.cfi_restore r7
bx lr
END(strcmp_krait)