mirror of
https://sourceware.org/git/glibc.git
synced 2024-11-30 00:31:08 +00:00
16d2ea4c82
This patch introduces a test to make sure no function modifies the xmm/ymm registers. With the exception of the auditing functions. The test is probably too pessimistic. All code linked into ld.so is checked. Perhaps at some point the callgraph starting from _dl_fixup and _dl_profile_fixup is checked and we can start using faster SSE-using functions in parts of ld.so.
292 lines
11 KiB
ArmAsm
292 lines
11 KiB
ArmAsm
/* strchr (str, ch) -- Return pointer to first occurrence of CH in STR.
|
|
For AMD x86-64.
|
|
Copyright (C) 2002, 2005 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, write to the Free
|
|
Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
|
|
02111-1307 USA. */
|
|
|
|
#include <sysdep.h>
|
|
#include "asm-syntax.h"
|
|
#include "bp-sym.h"
|
|
#include "bp-asm.h"
|
|
|
|
|
|
.text
|
|
ENTRY (BP_SYM (strchr))
|
|
|
|
/* Before we start with the main loop we process single bytes
|
|
until the source pointer is aligned. This has two reasons:
|
|
1. aligned 64-bit memory access is faster
|
|
and (more important)
|
|
2. we process in the main loop 64 bit in one step although
|
|
we don't know the end of the string. But accessing at
|
|
8-byte alignment guarantees that we never access illegal
|
|
memory if this would not also be done by the trivial
|
|
implementation (this is because all processor inherent
|
|
boundaries are multiples of 8). */
|
|
|
|
movq %rdi, %rdx
|
|
andl $7, %edx /* Mask alignment bits */
|
|
movq %rdi, %rax /* duplicate destination. */
|
|
jz 1f /* aligned => start loop */
|
|
neg %edx
|
|
addl $8, %edx /* Align to 8 bytes. */
|
|
|
|
/* Search the first bytes directly. */
|
|
0: movb (%rax), %cl /* load byte */
|
|
cmpb %cl,%sil /* compare byte. */
|
|
je 6f /* target found */
|
|
testb %cl,%cl /* is byte NUL? */
|
|
je 7f /* yes => return NULL */
|
|
incq %rax /* increment pointer */
|
|
decl %edx
|
|
jnz 0b
|
|
|
|
|
|
1:
|
|
/* At the moment %rsi contains C. What we need for the
|
|
algorithm is C in all bytes of the register. Avoid
|
|
operations on 16 bit words because these require an
|
|
prefix byte (and one more cycle). */
|
|
/* Populate 8 bit data to full 64-bit. */
|
|
movabs $0x0101010101010101,%r9
|
|
movzbl %sil,%edx
|
|
imul %rdx,%r9
|
|
|
|
movq $0xfefefefefefefeff, %r8 /* Save magic. */
|
|
|
|
/* We exit the loop if adding MAGIC_BITS to LONGWORD fails to
|
|
change any of the hole bits of LONGWORD.
|
|
|
|
1) Is this safe? Will it catch all the zero bytes?
|
|
Suppose there is a byte with all zeros. Any carry bits
|
|
propagating from its left will fall into the hole at its
|
|
least significant bit and stop. Since there will be no
|
|
carry from its most significant bit, the LSB of the
|
|
byte to the left will be unchanged, and the zero will be
|
|
detected.
|
|
|
|
2) Is this worthwhile? Will it ignore everything except
|
|
zero bytes? Suppose every byte of QUARDWORD has a bit set
|
|
somewhere. There will be a carry into bit 8. If bit 8
|
|
is set, this will carry into bit 16. If bit 8 is clear,
|
|
one of bits 9-15 must be set, so there will be a carry
|
|
into bit 16. Similarly, there will be a carry into bit
|
|
24 tec.. If one of bits 54-63 is set, there will be a carry
|
|
into bit 64 (=carry flag), so all of the hole bits will
|
|
be changed.
|
|
|
|
3) But wait! Aren't we looking for C, not zero?
|
|
Good point. So what we do is XOR LONGWORD with a longword,
|
|
each of whose bytes is C. This turns each byte that is C
|
|
into a zero. */
|
|
|
|
.p2align 4
|
|
4:
|
|
/* Main Loop is unrolled 4 times. */
|
|
/* First unroll. */
|
|
movq (%rax), %rcx /* get double word (= 8 bytes) in question */
|
|
addq $8,%rax /* adjust pointer for next word */
|
|
movq %r8, %rdx /* magic value */
|
|
xorq %r9, %rcx /* XOR with qword c|...|c => bytes of str == c
|
|
are now 0 */
|
|
addq %rcx, %rdx /* add the magic value to the word. We get
|
|
carry bits reported for each byte which
|
|
is *not* 0 */
|
|
jnc 3f /* highest byte is NUL => return pointer */
|
|
xorq %rcx, %rdx /* (word+magic)^word */
|
|
orq %r8, %rdx /* set all non-carry bits */
|
|
incq %rdx /* add 1: if one carry bit was *not* set
|
|
the addition will not result in 0. */
|
|
jnz 3f /* found c => return pointer */
|
|
|
|
/* The quadword we looked at does not contain the value we're looking
|
|
for. Let's search now whether we have reached the end of the
|
|
string. */
|
|
xorq %r9, %rcx /* restore original dword without reload */
|
|
movq %r8, %rdx /* magic value */
|
|
addq %rcx, %rdx /* add the magic value to the word. We get
|
|
carry bits reported for each byte which
|
|
is *not* 0 */
|
|
jnc 7f /* highest byte is NUL => return NULL */
|
|
xorq %rcx, %rdx /* (word+magic)^word */
|
|
orq %r8, %rdx /* set all non-carry bits */
|
|
incq %rdx /* add 1: if one carry bit was *not* set
|
|
the addition will not result in 0. */
|
|
jnz 7f /* found NUL => return NULL */
|
|
|
|
/* Second unroll. */
|
|
movq (%rax), %rcx /* get double word (= 8 bytes) in question */
|
|
addq $8,%rax /* adjust pointer for next word */
|
|
movq %r8, %rdx /* magic value */
|
|
xorq %r9, %rcx /* XOR with qword c|...|c => bytes of str == c
|
|
are now 0 */
|
|
addq %rcx, %rdx /* add the magic value to the word. We get
|
|
carry bits reported for each byte which
|
|
is *not* 0 */
|
|
jnc 3f /* highest byte is NUL => return pointer */
|
|
xorq %rcx, %rdx /* (word+magic)^word */
|
|
orq %r8, %rdx /* set all non-carry bits */
|
|
incq %rdx /* add 1: if one carry bit was *not* set
|
|
the addition will not result in 0. */
|
|
jnz 3f /* found c => return pointer */
|
|
|
|
/* The quadword we looked at does not contain the value we're looking
|
|
for. Let's search now whether we have reached the end of the
|
|
string. */
|
|
xorq %r9, %rcx /* restore original dword without reload */
|
|
movq %r8, %rdx /* magic value */
|
|
addq %rcx, %rdx /* add the magic value to the word. We get
|
|
carry bits reported for each byte which
|
|
is *not* 0 */
|
|
jnc 7f /* highest byte is NUL => return NULL */
|
|
xorq %rcx, %rdx /* (word+magic)^word */
|
|
orq %r8, %rdx /* set all non-carry bits */
|
|
incq %rdx /* add 1: if one carry bit was *not* set
|
|
the addition will not result in 0. */
|
|
jnz 7f /* found NUL => return NULL */
|
|
/* Third unroll. */
|
|
movq (%rax), %rcx /* get double word (= 8 bytes) in question */
|
|
addq $8,%rax /* adjust pointer for next word */
|
|
movq %r8, %rdx /* magic value */
|
|
xorq %r9, %rcx /* XOR with qword c|...|c => bytes of str == c
|
|
are now 0 */
|
|
addq %rcx, %rdx /* add the magic value to the word. We get
|
|
carry bits reported for each byte which
|
|
is *not* 0 */
|
|
jnc 3f /* highest byte is NUL => return pointer */
|
|
xorq %rcx, %rdx /* (word+magic)^word */
|
|
orq %r8, %rdx /* set all non-carry bits */
|
|
incq %rdx /* add 1: if one carry bit was *not* set
|
|
the addition will not result in 0. */
|
|
jnz 3f /* found c => return pointer */
|
|
|
|
/* The quadword we looked at does not contain the value we're looking
|
|
for. Let's search now whether we have reached the end of the
|
|
string. */
|
|
xorq %r9, %rcx /* restore original dword without reload */
|
|
movq %r8, %rdx /* magic value */
|
|
addq %rcx, %rdx /* add the magic value to the word. We get
|
|
carry bits reported for each byte which
|
|
is *not* 0 */
|
|
jnc 7f /* highest byte is NUL => return NULL */
|
|
xorq %rcx, %rdx /* (word+magic)^word */
|
|
orq %r8, %rdx /* set all non-carry bits */
|
|
incq %rdx /* add 1: if one carry bit was *not* set
|
|
the addition will not result in 0. */
|
|
jnz 7f /* found NUL => return NULL */
|
|
/* Fourth unroll. */
|
|
movq (%rax), %rcx /* get double word (= 8 bytes) in question */
|
|
addq $8,%rax /* adjust pointer for next word */
|
|
movq %r8, %rdx /* magic value */
|
|
xorq %r9, %rcx /* XOR with qword c|...|c => bytes of str == c
|
|
are now 0 */
|
|
addq %rcx, %rdx /* add the magic value to the word. We get
|
|
carry bits reported for each byte which
|
|
is *not* 0 */
|
|
jnc 3f /* highest byte is NUL => return pointer */
|
|
xorq %rcx, %rdx /* (word+magic)^word */
|
|
orq %r8, %rdx /* set all non-carry bits */
|
|
incq %rdx /* add 1: if one carry bit was *not* set
|
|
the addition will not result in 0. */
|
|
jnz 3f /* found c => return pointer */
|
|
|
|
/* The quadword we looked at does not contain the value we're looking
|
|
for. Let's search now whether we have reached the end of the
|
|
string. */
|
|
xorq %r9, %rcx /* restore original dword without reload */
|
|
movq %r8, %rdx /* magic value */
|
|
addq %rcx, %rdx /* add the magic value to the word. We get
|
|
carry bits reported for each byte which
|
|
is *not* 0 */
|
|
jnc 7f /* highest byte is NUL => return NULL */
|
|
xorq %rcx, %rdx /* (word+magic)^word */
|
|
orq %r8, %rdx /* set all non-carry bits */
|
|
incq %rdx /* add 1: if one carry bit was *not* set
|
|
the addition will not result in 0. */
|
|
jz 4b /* no NUL found => restart loop */
|
|
|
|
|
|
7: /* Return NULL. */
|
|
xorl %eax, %eax
|
|
retq
|
|
|
|
|
|
/* We now scan for the byte in which the character was matched.
|
|
But we have to take care of the case that a NUL char is
|
|
found before this in the dword. Note that we XORed %rcx
|
|
with the byte we're looking for, therefore the tests below look
|
|
reversed. */
|
|
|
|
|
|
.p2align 4 /* Align, it's a jump target. */
|
|
3: movq %r9,%rdx /* move to %rdx so that we can access bytes */
|
|
subq $8,%rax /* correct pointer increment. */
|
|
testb %cl, %cl /* is first byte C? */
|
|
jz 6f /* yes => return pointer */
|
|
cmpb %dl, %cl /* is first byte NUL? */
|
|
je 7b /* yes => return NULL */
|
|
incq %rax /* increment pointer */
|
|
|
|
testb %ch, %ch /* is second byte C? */
|
|
jz 6f /* yes => return pointer */
|
|
cmpb %dl, %ch /* is second byte NUL? */
|
|
je 7b /* yes => return NULL? */
|
|
incq %rax /* increment pointer */
|
|
|
|
shrq $16, %rcx /* make upper bytes accessible */
|
|
testb %cl, %cl /* is third byte C? */
|
|
jz 6f /* yes => return pointer */
|
|
cmpb %dl, %cl /* is third byte NUL? */
|
|
je 7b /* yes => return NULL */
|
|
incq %rax /* increment pointer */
|
|
|
|
testb %ch, %ch /* is fourth byte C? */
|
|
jz 6f /* yes => return pointer */
|
|
cmpb %dl, %ch /* is fourth byte NUL? */
|
|
je 7b /* yes => return NULL? */
|
|
incq %rax /* increment pointer */
|
|
|
|
shrq $16, %rcx /* make upper bytes accessible */
|
|
testb %cl, %cl /* is fifth byte C? */
|
|
jz 6f /* yes => return pointer */
|
|
cmpb %dl, %cl /* is fifth byte NUL? */
|
|
je 7b /* yes => return NULL */
|
|
incq %rax /* increment pointer */
|
|
|
|
testb %ch, %ch /* is sixth byte C? */
|
|
jz 6f /* yes => return pointer */
|
|
cmpb %dl, %ch /* is sixth byte NUL? */
|
|
je 7b /* yes => return NULL? */
|
|
incq %rax /* increment pointer */
|
|
|
|
shrq $16, %rcx /* make upper bytes accessible */
|
|
testb %cl, %cl /* is seventh byte C? */
|
|
jz 6f /* yes => return pointer */
|
|
cmpb %dl, %cl /* is seventh byte NUL? */
|
|
je 7b /* yes => return NULL */
|
|
|
|
/* It must be in the eigth byte and it cannot be NUL. */
|
|
incq %rax
|
|
|
|
6:
|
|
nop
|
|
retq
|
|
END (BP_SYM (strchr))
|
|
|
|
weak_alias (BP_SYM (strchr), BP_SYM (index))
|
|
libc_hidden_builtin_def (strchr)
|