+++ /dev/null
-/* strchr (str, ch) -- Return pointer to first occurrence of CH in STR.
- For AMD x86-64.
- Copyright (C) 2002-2015 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>
-#include "asm-syntax.h"
-
-
- .text
-ENTRY (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 (strchr)
-
-weak_alias (strchr, index)
-libc_hidden_builtin_def (strchr)
+++ /dev/null
-/* strlen(str) -- determine the length of the string STR.
- Copyright (C) 2002-2015 Free Software Foundation, Inc.
- Based on i486 version contributed by Ulrich Drepper <drepper@redhat.com>.
- 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>
-#include "asm-syntax.h"
-
-
- .text
-ENTRY (strlen)
- movq %rdi, %rcx /* Duplicate source pointer. */
- andl $7, %ecx /* mask alignment bits */
- movq %rdi, %rax /* duplicate destination. */
- jz 1f /* aligned => start loop */
-
- neg %ecx /* We need to align to 8 bytes. */
- addl $8,%ecx
- /* Search the first bytes directly. */
-0: cmpb $0x0,(%rax) /* is byte NUL? */
- je 2f /* yes => return */
- incq %rax /* increment pointer */
- decl %ecx
- jnz 0b
-
-1: movq $0xfefefefefefefeff,%r8 /* Save magic. */
-
- .p2align 4 /* Align loop. */
-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 */
- 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 NUL => return pointer */
-
- /* 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 */
- 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 NUL => return pointer */
-
- /* 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 */
- 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 NUL => return pointer */
-
- /* 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 */
- 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. */
- jz 4b /* no NUL found => continue loop */
-
- .p2align 4 /* Align, it's a jump target. */
-3: subq $8,%rax /* correct pointer increment. */
-
- testb %cl, %cl /* is first byte NUL? */
- jz 2f /* yes => return */
- incq %rax /* increment pointer */
-
- testb %ch, %ch /* is second byte NUL? */
- jz 2f /* yes => return */
- incq %rax /* increment pointer */
-
- testl $0x00ff0000, %ecx /* is third byte NUL? */
- jz 2f /* yes => return pointer */
- incq %rax /* increment pointer */
-
- testl $0xff000000, %ecx /* is fourth byte NUL? */
- jz 2f /* yes => return pointer */
- incq %rax /* increment pointer */
-
- shrq $32, %rcx /* look at other half. */
-
- testb %cl, %cl /* is first byte NUL? */
- jz 2f /* yes => return */
- incq %rax /* increment pointer */
-
- testb %ch, %ch /* is second byte NUL? */
- jz 2f /* yes => return */
- incq %rax /* increment pointer */
-
- testl $0xff0000, %ecx /* is third byte NUL? */
- jz 2f /* yes => return pointer */
- incq %rax /* increment pointer */
-2:
- subq %rdi, %rax /* compute difference to string start */
- ret
-END (strlen)
-libc_hidden_builtin_def (strlen)
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