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Diffstat (limited to 'libc/string/x86_64/strcat.S')
-rw-r--r--libc/string/x86_64/strcat.S256
1 files changed, 256 insertions, 0 deletions
diff --git a/libc/string/x86_64/strcat.S b/libc/string/x86_64/strcat.S
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+++ b/libc/string/x86_64/strcat.S
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+/* strcat(dest, src) -- Append SRC on the end of DEST.
+ Optimized for x86-64.
+ Copyright (C) 2002 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+ Contributed by Andreas Jaeger <aj@suse.de>, 2002.
+
+ 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 "_glibc_inc.h"
+
+
+ .text
+ENTRY (BP_SYM (strcat))
+ movq %rdi, %rcx /* Dest. register. */
+ andl $7, %ecx /* mask alignment bits */
+ movq %rdi, %rax /* Duplicate destination pointer. */
+ movq $0xfefefefefefefeff,%r8
+
+ /* First step: Find end of destination. */
+ jz 4f /* 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 => start copy */
+ incq %rax /* increment pointer */
+ decl %ecx
+ jnz 0b
+
+
+
+ /* Now the source is aligned. Scan for NUL byte. */
+ .p2align 4
+4:
+ /* 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:
+ /* Second step: Copy source to destination. */
+
+ movq %rsi, %rcx /* duplicate */
+ andl $7,%ecx /* mask alignment bits */
+ movq %rax, %rdx /* move around */
+ jz 22f /* aligned => start loop */
+
+ neg %ecx /* align to 8 bytes. */
+ addl $8, %ecx
+ /* Align the source pointer. */
+21:
+ movb (%rsi), %al /* Fetch a byte */
+ testb %al, %al /* Is it NUL? */
+ movb %al, (%rdx) /* Store it */
+ jz 24f /* If it was NUL, done! */
+ incq %rsi
+ incq %rdx
+ decl %ecx
+ jnz 21b
+
+ /* Now the sources is aligned. Unfortunatly we cannot force
+ to have both source and destination aligned, so ignore the
+ alignment of the destination. */
+ .p2align 4
+22:
+ /* 1st unroll. */
+ movq (%rsi), %rax /* Read double word (8 bytes). */
+ addq $8, %rsi /* Adjust pointer for next word. */
+ movq %rax, %r9 /* Save a copy for NUL finding. */
+ addq %r8, %r9 /* add the magic value to the word. We get
+ carry bits reported for each byte which
+ is *not* 0 */
+ jnc 23f /* highest byte is NUL => return pointer */
+ xorq %rax, %r9 /* (word+magic)^word */
+ orq %r8, %r9 /* set all non-carry bits */
+ incq %r9 /* add 1: if one carry bit was *not* set
+ the addition will not result in 0. */
+
+ jnz 23f /* found NUL => return pointer */
+
+ movq %rax, (%rdx) /* Write value to destination. */
+ addq $8, %rdx /* Adjust pointer. */
+
+ /* 2nd unroll. */
+ movq (%rsi), %rax /* Read double word (8 bytes). */
+ addq $8, %rsi /* Adjust pointer for next word. */
+ movq %rax, %r9 /* Save a copy for NUL finding. */
+ addq %r8, %r9 /* add the magic value to the word. We get
+ carry bits reported for each byte which
+ is *not* 0 */
+ jnc 23f /* highest byte is NUL => return pointer */
+ xorq %rax, %r9 /* (word+magic)^word */
+ orq %r8, %r9 /* set all non-carry bits */
+ incq %r9 /* add 1: if one carry bit was *not* set
+ the addition will not result in 0. */
+
+ jnz 23f /* found NUL => return pointer */
+
+ movq %rax, (%rdx) /* Write value to destination. */
+ addq $8, %rdx /* Adjust pointer. */
+
+ /* 3rd unroll. */
+ movq (%rsi), %rax /* Read double word (8 bytes). */
+ addq $8, %rsi /* Adjust pointer for next word. */
+ movq %rax, %r9 /* Save a copy for NUL finding. */
+ addq %r8, %r9 /* add the magic value to the word. We get
+ carry bits reported for each byte which
+ is *not* 0 */
+ jnc 23f /* highest byte is NUL => return pointer */
+ xorq %rax, %r9 /* (word+magic)^word */
+ orq %r8, %r9 /* set all non-carry bits */
+ incq %r9 /* add 1: if one carry bit was *not* set
+ the addition will not result in 0. */
+
+ jnz 23f /* found NUL => return pointer */
+
+ movq %rax, (%rdx) /* Write value to destination. */
+ addq $8, %rdx /* Adjust pointer. */
+
+ /* 4th unroll. */
+ movq (%rsi), %rax /* Read double word (8 bytes). */
+ addq $8, %rsi /* Adjust pointer for next word. */
+ movq %rax, %r9 /* Save a copy for NUL finding. */
+ addq %r8, %r9 /* add the magic value to the word. We get
+ carry bits reported for each byte which
+ is *not* 0 */
+ jnc 23f /* highest byte is NUL => return pointer */
+ xorq %rax, %r9 /* (word+magic)^word */
+ orq %r8, %r9 /* set all non-carry bits */
+ incq %r9 /* add 1: if one carry bit was *not* set
+ the addition will not result in 0. */
+
+ jnz 23f /* found NUL => return pointer */
+
+ movq %rax, (%rdx) /* Write value to destination. */
+ addq $8, %rdx /* Adjust pointer. */
+ jmp 22b /* Next iteration. */
+
+ /* Do the last few bytes. %rax contains the value to write.
+ The loop is unrolled twice. */
+ .p2align 4
+23:
+ movb %al, (%rdx) /* 1st byte. */
+ testb %al, %al /* Is it NUL. */
+ jz 24f /* yes, finish. */
+ incq %rdx /* Increment destination. */
+ movb %ah, (%rdx) /* 2nd byte. */
+ testb %ah, %ah /* Is it NUL?. */
+ jz 24f /* yes, finish. */
+ incq %rdx /* Increment destination. */
+ shrq $16, %rax /* Shift... */
+ jmp 23b /* and look at next two bytes in %rax. */
+
+
+24:
+ movq %rdi, %rax /* Source is return value. */
+ retq
+END (BP_SYM (strcat))