| /* 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 <sysdep.h> |
| #include "asm-syntax.h" |
| #include "bp-sym.h" |
| #include "bp-asm.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)) |
| libc_hidden_builtin_def (strcat) |
