diff options
Diffstat (limited to 'sysdeps/powerpc/powerpc32/power7/strlen.S')
| -rw-r--r-- | sysdeps/powerpc/powerpc32/power7/strlen.S | 98 |
1 files changed, 98 insertions, 0 deletions
diff --git a/sysdeps/powerpc/powerpc32/power7/strlen.S b/sysdeps/powerpc/powerpc32/power7/strlen.S new file mode 100644 index 0000000000..976359b3f9 --- /dev/null +++ b/sysdeps/powerpc/powerpc32/power7/strlen.S @@ -0,0 +1,98 @@ +/* Optimized strlen implementation for PowerPC32 using cmpb. + Copyright (C) 2010 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, write to the Free + Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston MA + 02110-1301 USA. */ + +#include <sysdep.h> +#include <bp-sym.h> +#include <bp-asm.h> + +/* int [r3] strlen (char *s [r3]) */ + .machine power7 +ENTRY (BP_SYM (strlen)) + CALL_MCOUNT + dcbt 0,r3 + clrrwi r4,r3,2 /* Align the address to word boundary. */ + rlwinm r6,r3,3,27,28 /* Calculate padding. */ + li r0,0 /* Word with null chars to use with cmpb. */ + li r5,-1 /* MASK = 0xffffffffffffffff. */ + lwz r12,0(r4) /* Load word from memory. */ + srw r5,r5,r6 /* MASK = MASK >> padding. */ + orc r9,r12,r5 /* Mask bits that are not part of the string. */ + cmpb r10,r9,r0 /* Check for null bytes in WORD1. */ + cmpwi 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 doubleword boundary? If so, skip to + the main loop. Otherwise, go through the alignment code. */ + + bt 29,L(loop) + + /* Handle WORD2 of pair. */ + lwzu r12,4(r4) + cmpb r10,r12,r0 + cmpwi cr7,r10,0 + bne cr7,L(done) + b L(loop) /* We branch here (rather than falling through) + to skip the nops due to heavy alignment + of the loop below. */ + + /* 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 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(r4) + lwzu r11, 8(r4) + cmpb r10,r12,r0 + cmpb r9,r11,r0 + or r8,r9,r10 /* Merge everything in one word. */ + cmpwi cr7,r8,0 + beq cr7,L(loop) + + /* 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. */ + + cmpwi cr6,r10,0 + addi r4,r4,-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 r4,r4,4 + + /* 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. */ +L(done): + cntlzw r0,r10 /* Count leading zeroes before the match. */ + subf r5,r3,r4 + srwi r0,r0,3 /* Convert leading zeroes to bytes. */ + add r3,r5,r0 /* Compute final length. */ + blr +END (BP_SYM (strlen)) +libc_hidden_builtin_def (strlen) |