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-rw-r--r--libc/string/x86_64/strcpy.S153
1 files changed, 153 insertions, 0 deletions
diff --git a/libc/string/x86_64/strcpy.S b/libc/string/x86_64/strcpy.S
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+/* strcpy/stpcpy implementation 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"
+
+#ifndef USE_AS_STPCPY
+# define STRCPY strcpy
+#endif
+
+ .text
+ENTRY (BP_SYM (STRCPY))
+ movq %rsi, %rcx /* Source register. */
+ andl $7, %ecx /* mask alignment bits */
+ movq %rdi, %rdx /* Duplicate destination pointer. */
+
+ jz 5f /* aligned => start loop */
+
+ neg %ecx /* We need to align to 8 bytes. */
+ addl $8,%ecx
+ /* Search the first bytes directly. */
+0:
+ movb (%rsi), %al /* Fetch a byte */
+ testb %al, %al /* Is it NUL? */
+ movb %al, (%rdx) /* Store it */
+ jz 4f /* If it was NUL, done! */
+ incq %rsi
+ incq %rdx
+ decl %ecx
+ jnz 0b
+
+5:
+ movq $0xfefefefefefefeff,%r8
+
+ /* 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
+1:
+ /* 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 3f /* 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 3f /* 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 3f /* 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 3f /* 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 3f /* 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 3f /* 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 3f /* 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 3f /* found NUL => return pointer */
+
+ movq %rax, (%rdx) /* Write value to destination. */
+ addq $8, %rdx /* Adjust pointer. */
+ jmp 1b /* Next iteration. */
+
+ /* Do the last few bytes. %rax contains the value to write.
+ The loop is unrolled twice. */
+ .p2align 4
+3:
+ /* Note that stpcpy needs to return with the value of the NUL
+ byte. */
+ movb %al, (%rdx) /* 1st byte. */
+ testb %al, %al /* Is it NUL. */
+ jz 4f /* yes, finish. */
+ incq %rdx /* Increment destination. */
+ movb %ah, (%rdx) /* 2nd byte. */
+ testb %ah, %ah /* Is it NUL?. */
+ jz 4f /* yes, finish. */
+ incq %rdx /* Increment destination. */
+ shrq $16, %rax /* Shift... */
+ jmp 3b /* and look at next two bytes in %rax. */
+
+4:
+#ifdef USE_AS_STPCPY
+ movq %rdx, %rax /* Destination is return value. */
+#else
+ movq %rdi, %rax /* Source is return value. */
+#endif
+ retq
+END (BP_SYM (STRCPY))