| /* Optimized strlen implementation for PowerPC64/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] strlen (char *s [r3]) */ |
| |
| #ifndef STRLEN |
| # define STRLEN strlen |
| #endif |
| DOT_MACHINE ("power7") |
| ENTRY_TOCLESS (STRLEN) |
| CALL_MCOUNT 1 |
| dcbt 0,r3 |
| clrrdi r4,r3,3 /* Align the address to doubleword boundary. */ |
| rlwinm r6,r3,3,26,28 /* Calculate padding. */ |
| li r0,0 /* Doubleword with null chars to use |
| with cmpb. */ |
| li r5,-1 /* MASK = 0xffffffffffffffff. */ |
| ld r12,0(r4) /* Load doubleword from memory. */ |
| #ifdef __LITTLE_ENDIAN__ |
| sld r5,r5,r6 |
| #else |
| srd r5,r5,r6 /* MASK = MASK >> padding. */ |
| #endif |
| orc r9,r12,r5 /* Mask bits that are not part of the string. */ |
| cmpb r10,r9,r0 /* Check for null bytes in DWORD1. */ |
| cmpdi cr7,r10,0 /* If r10 == 0, no null's have been found. */ |
| bne cr7,L(done) |
| |
| mtcrf 0x01,r4 |
| |
| /* Are we now aligned to a quadword boundary? If so, skip to |
| the main loop. Otherwise, go through the alignment code. */ |
| |
| bt 28,L(loop) |
| |
| /* Handle DWORD2 of pair. */ |
| ldu r12,8(r4) |
| cmpb r10,r12,r0 |
| cmpdi cr7,r10,0 |
| bne cr7,L(done) |
| |
| /* Main loop to look for the end of the string. Since it's a |
| small loop (< 8 instructions), align it to 32-bytes. */ |
| .p2align 5 |
| L(loop): |
| /* Load two doublewords, compare and merge in a |
| single register for speed. This is an attempt |
| to speed up the null-checking process for bigger strings. */ |
| |
| ld r12, 8(r4) |
| ldu r11, 16(r4) |
| cmpb r10,r12,r0 |
| cmpb r9,r11,r0 |
| or r8,r9,r10 /* Merge everything in one doubleword. */ |
| cmpdi cr7,r8,0 |
| beq cr7,L(loop) |
| |
| /* OK, one (or both) of the doublewords contains a null byte. Check |
| the first doubleword and decrement the address in case the first |
| doubleword really contains a null byte. */ |
| |
| cmpdi cr6,r10,0 |
| addi r4,r4,-8 |
| bne cr6,L(done) |
| |
| /* The null byte must be in the second doubleword. Adjust the address |
| again and move the result of cmpb to r10 so we can calculate the |
| length. */ |
| |
| mr r10,r9 |
| addi r4,r4,8 |
| |
| /* r10 has the output of the cmpb instruction, that is, it contains |
| 0xff in the same position as the null byte in the original |
| doubleword from the string. Use that to calculate the length. */ |
| L(done): |
| #ifdef __LITTLE_ENDIAN__ |
| addi r9, r10, -1 /* Form a mask from trailing zeros. */ |
| andc r9, r9, r10 |
| popcntd r0, r9 /* Count the bits in the mask. */ |
| #else |
| cntlzd r0,r10 /* Count leading zeros before the match. */ |
| #endif |
| subf r5,r3,r4 |
| srdi r0,r0,3 /* Convert leading/trailing zeros to bytes. */ |
| add r3,r5,r0 /* Compute final length. */ |
| blr |
| END (STRLEN) |
| libc_hidden_builtin_def (strlen) |