projects / thirdparty / glibc.git / blame
| Commit | Line | Data |
|---|---|---|
| 5929563f | 1 | /* Copy SRC to DEST returning the address of the terminating '\0' in DEST. |
| 6d52618b | 2 | For Intel 80x86, x>=3. |
| d4697bc9 | 3 | Copyright (C) 1994-2014 Free Software Foundation, Inc. |
| 6d52618b UD |
4 | This file is part of the GNU C Library. |
| 5 | Contributed by Ulrich Drepper (drepper@gnu.ai.mit.edu). | |
| 6 | ||
| 7 | The GNU C Library is free software; you can redistribute it and/or | |
| 41bdb6e2 AJ |
8 | modify it under the terms of the GNU Lesser General Public |
| 9 | License as published by the Free Software Foundation; either | |
| 10 | version 2.1 of the License, or (at your option) any later version. | |
| 6d52618b UD |
11 | |
| 12 | The GNU C Library is distributed in the hope that it will be useful, | |
| 13 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
| 14 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
| 41bdb6e2 | 15 | Lesser General Public License for more details. |
| 6d52618b | 16 | |
| 41bdb6e2 | 17 | You should have received a copy of the GNU Lesser General Public |
| 59ba27a6 PE |
18 | License along with the GNU C Library; if not, see |
| 19 | <http://www.gnu.org/licenses/>. */ | |
| 8f5ca04b RM |
20 | |
| 21 | /* This function is defined neither in ANSI nor POSIX standards but is | |
| 22 | also not invented here. */ | |
| 23 | ||
| 24 | #include <sysdep.h> | |
| 25 | #include "asm-syntax.h" | |
| 26 | ||
| 2366713d | 27 | #define PARMS 4 /* no space for saved regs */ |
| 3f02f778 | 28 | #define RTN PARMS |
| 2366713d JM |
29 | #define DEST RTN |
| 30 | #define SRC DEST+4 | |
| 8f5ca04b RM |
31 | |
| 32 | .text | |
| 2366713d | 33 | ENTRY (__stpcpy) |
| 8f5ca04b | 34 | |
| 3f02f778 GM |
35 | movl DEST(%esp), %eax |
| 36 | movl SRC(%esp), %ecx | |
| 8f5ca04b RM |
37 | subl %eax, %ecx /* magic: reduce number of loop variants |
| 38 | to one using addressing mode */ | |
| 39 | ||
| 40 | /* Here we would like to write | |
| 41 | ||
| 42 | subl $4, %eax | |
| 43 | ALIGN (4) | |
| 44 | ||
| 45 | but the assembler is too smart and optimizes for the shortest | |
| 46 | form where the number only needs one byte. But if we could | |
| 47 | have the long form we would not need the alignment. */ | |
| 48 | ||
| 49 | .byte 0x81, 0xe8 /* This is `subl $0x00000004, %eax' */ | |
| 50 | .long 0x00000004 | |
| 51 | ||
| 52 | /* Four times unfolded loop with only one loop counter. This | |
| 6d52618b | 53 | is achieved by the use of index+base addressing mode. As the |
| 8f5ca04b RM |
54 | loop counter we use the destination address because this is |
| 55 | also the result. */ | |
| 5929563f | 56 | L(1): addl $4, %eax /* increment loop counter */ |
| 8f5ca04b RM |
57 | |
| 58 | movb (%eax,%ecx), %dl /* load current char */ | |
| 59 | movb %dl, (%eax) /* and store it */ | |
| 60 | testb %dl, %dl /* was it NUL? */ | |
| 5929563f | 61 | jz L(2) /* yes, then exit */ |
| 8f5ca04b RM |
62 | |
| 63 | movb 1(%eax,%ecx), %dl /* load current char */ | |
| 64 | movb %dl, 1(%eax) /* and store it */ | |
| 65 | testb %dl, %dl /* was it NUL? */ | |
| 5929563f | 66 | jz L(3) /* yes, then exit */ |
| 8f5ca04b RM |
67 | |
| 68 | movb 2(%eax,%ecx), %dl /* load current char */ | |
| 69 | movb %dl, 2(%eax) /* and store it */ | |
| 70 | testb %dl, %dl /* was it NUL? */ | |
| 5929563f | 71 | jz L(4) /* yes, then exit */ |
| 8f5ca04b RM |
72 | |
| 73 | movb 3(%eax,%ecx), %dl /* load current char */ | |
| 74 | movb %dl, 3(%eax) /* and store it */ | |
| 75 | testb %dl, %dl /* was it NUL? */ | |
| 5929563f | 76 | jnz L(1) /* no, then continue loop */ |
| 8f5ca04b RM |
77 | |
| 78 | incl %eax /* correct loop counter */ | |
| 5929563f UD |
79 | L(4): incl %eax |
| 80 | L(3): incl %eax | |
| 81 | L(2): | |
| 3f02f778 | 82 | |
| 2366713d JM |
83 | ret |
| 84 | END (__stpcpy) | |
| 8f5ca04b | 85 | |
| 2366713d | 86 | weak_alias (__stpcpy, stpcpy) |
| 6111cd0e | 87 | libc_hidden_def (__stpcpy) |
| 3dbfd811 | 88 | libc_hidden_builtin_def (stpcpy) |