| /* Optimized strnlen implementation for PowerPC32/POWER7 using cmpb insn. |
| Copyright (C) 2010-2018 Free Software Foundation, Inc. |
| Contributed by Luis Machado <luisgpm@br.ibm.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> |
| |
| /* int [r3] strnlen (char *s [r3], int size [r4]) */ |
| .machine power7 |
| ENTRY (__strnlen) |
| CALL_MCOUNT |
| dcbt 0,r3 |
| clrrwi r8,r3,2 /* Align the address to word boundary. */ |
| add r7,r3,r4 /* Calculate the last acceptable address. */ |
| cmplwi r4,16 |
| li r0,0 /* Word with null chars. */ |
| addi r7,r7,-1 |
| ble L(small_range) |
| |
| rlwinm r6,r3,3,27,28 /* Calculate padding. */ |
| lwz r12,0(r8) /* Load word from memory. */ |
| cmpb r10,r12,r0 /* Check for null bytes in DWORD1. */ |
| #ifdef __LITTLE_ENDIAN__ |
| srw r10,r10,r6 |
| slw r10,r10,r6 |
| #else |
| slw r10,r10,r6 |
| srw r10,r10,r6 |
| #endif |
| cmplwi cr7,r10,0 /* If r10 == 0, no null's have been found. */ |
| bne cr7,L(done) |
| |
| clrrwi r7,r7,2 /* Address of last word. */ |
| mtcrf 0x01,r8 |
| /* Are we now aligned to a doubleword boundary? If so, skip to |
| the main loop. Otherwise, go through the alignment code. */ |
| |
| bt 29,L(loop_setup) |
| |
| /* Handle WORD2 of pair. */ |
| lwzu r12,4(r8) |
| cmpb r10,r12,r0 |
| cmplwi cr7,r10,0 |
| bne cr7,L(done) |
| |
| L(loop_setup): |
| /* The last word we want to read in the loop below is the one |
| containing the last byte of the string, ie. the word at |
| (s + size - 1) & ~3, or r7. The first word read is at |
| r8 + 4, we read 2 * cnt words, so the last word read will |
| be at r8 + 4 + 8 * cnt - 4. Solving for cnt gives |
| cnt = (r7 - r8) / 8 */ |
| sub r5,r7,r8 |
| srwi r6,r5,3 /* Number of loop iterations. */ |
| mtctr r6 /* Setup the counter. */ |
| |
| /* Main loop to look for the null byte in the string. Since |
| it's a small loop (< 8 instructions), align it to 32-bytes. */ |
| .p2align 5 |
| L(loop): |
| /* Load two words, compare and merge in a |
| single register for speed. This is an attempt |
| to speed up the null-checking process for bigger strings. */ |
| |
| lwz r12,4(r8) |
| lwzu r11,8(r8) |
| cmpb r10,r12,r0 |
| cmpb r9,r11,r0 |
| or r5,r9,r10 /* Merge everything in one word. */ |
| cmplwi cr7,r5,0 |
| bne cr7,L(found) |
| bdnz L(loop) |
| |
| /* We may have one more word to read. */ |
| cmplw cr6,r8,r7 |
| beq cr6,L(end_max) |
| |
| lwzu r12,4(r8) |
| cmpb r10,r12,r0 |
| cmplwi cr6,r10,0 |
| bne cr6,L(done) |
| |
| L(end_max): |
| mr r3,r4 |
| blr |
| |
| /* OK, one (or both) of the words contains a null byte. Check |
| the first word and decrement the address in case the first |
| word really contains a null byte. */ |
| .align 4 |
| L(found): |
| cmplwi cr6,r10,0 |
| addi r8,r8,-4 |
| bne cr6,L(done) |
| |
| /* The null byte must be in the second word. Adjust the address |
| again and move the result of cmpb to r10 so we can calculate the |
| length. */ |
| |
| mr r10,r9 |
| addi r8,r8,4 |
| |
| /* r10 has the output of the cmpb instruction, that is, it contains |
| 0xff in the same position as the null byte in the original |
| word from the string. Use that to calculate the length. |
| We need to make sure the null char is *before* the end of the |
| range. */ |
| L(done): |
| #ifdef __LITTLE_ENDIAN__ |
| addi r0,r10,-1 |
| andc r0,r0,r10 |
| popcntw r0,r0 |
| #else |
| cntlzw r0,r10 /* Count leading zeros before the match. */ |
| #endif |
| sub r3,r8,r3 |
| srwi r0,r0,3 /* Convert leading/trailing zeros to bytes. */ |
| add r3,r3,r0 /* Length until the match. */ |
| cmplw r3,r4 |
| blelr |
| mr r3,r4 |
| blr |
| |
| /* Deals with size <= 16. */ |
| .align 4 |
| L(small_range): |
| cmplwi r4,0 |
| beq L(end_max) |
| |
| clrrwi r7,r7,2 /* Address of last word. */ |
| |
| rlwinm r6,r3,3,27,28 /* Calculate padding. */ |
| lwz r12,0(r8) /* Load word from memory. */ |
| cmpb r10,r12,r0 /* Check for null bytes in WORD1. */ |
| #ifdef __LITTLE_ENDIAN__ |
| srw r10,r10,r6 |
| slw r10,r10,r6 |
| #else |
| slw r10,r10,r6 |
| srw r10,r10,r6 |
| #endif |
| cmplwi cr7,r10,0 |
| bne cr7,L(done) |
| |
| cmplw r8,r7 |
| beq L(end_max) |
| |
| .p2align 5 |
| L(loop_small): |
| lwzu r12,4(r8) |
| cmpb r10,r12,r0 |
| cmplwi cr6,r10,0 |
| bne cr6,L(done) |
| cmplw r8,r7 |
| bne L(loop_small) |
| mr r3,r4 |
| blr |
| |
| END (__strnlen) |
| libc_hidden_def (__strnlen) |
| weak_alias (__strnlen, strnlen) |
| libc_hidden_builtin_def (strnlen) |
