diff options
Diffstat (limited to 'sysdeps/powerpc/powerpc32/power7/strnlen.S')
| -rw-r--r-- | sysdeps/powerpc/powerpc32/power7/strnlen.S | 172 |
1 files changed, 172 insertions, 0 deletions
diff --git a/sysdeps/powerpc/powerpc32/power7/strnlen.S b/sysdeps/powerpc/powerpc32/power7/strnlen.S new file mode 100644 index 0000000000..731a15d459 --- /dev/null +++ b/sysdeps/powerpc/powerpc32/power7/strnlen.S @@ -0,0 +1,172 @@ +/* Optimized strnlen 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] strnlen (char *s [r3], int size [r4]) */ + .machine power7 +ENTRY (BP_SYM (__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. */ + ble L(small_range) + + cmplw cr7,r3,r7 /* Is the address equal or less than r3? If + it's equal or less, it means size is either 0 + or a negative number. */ + ble cr7,L(proceed) + + li r7,-1 /* Make r11 the biggest if r4 <= 0. */ +L(proceed): + 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. */ + slw r10,r10,r6 + srw r10,r10,r6 + cmplwi cr7,r10,0 /* If r10 == 0, no null's have been found. */ + bne cr7,L(done) + + /* Are we done already? */ + addi r9,r8,4 + cmplw cr6,r9,r7 + bge cr6,L(end_max) + + 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 DWORD2 of pair. */ + lwzu r12,4(r8) + cmpb r10,r12,r0 + cmplwi cr7,r10,0 + bne cr7,L(done) + + /* Are we done already? */ + addi r9,r8,4 + cmplw cr6,r9,r7 + bge cr6,L(end_max) + +L(loop_setup): + sub r5,r7,r9 + srwi r6,r5,3 /* Number of loop iterations. */ + mtctr r6 /* Setup the counter. */ + b L(loop) + /* Main loop to look for the null byte backwards 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're here because the counter reached 0, and that means we + didn't have any matches for null in the whole range. Just return + the original size. */ + addi r9,r8,4 + cmplw cr6,r9,r7 + blt cr6,L(loop_small) + +L(end_max): + sub r3,r7,r3 + 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): + cntlzw r0,r10 /* Count leading zeroes before the match. */ + srwi r0,r0,3 /* Convert leading zeroes to bytes. */ + add r9,r8,r0 + sub r6,r9,r3 /* Length until the match. */ + cmplw r9,r7 + bgt L(end_max) + mr r3,r6 + blr + + .align 4 +L(zero): + li r3,0 + blr + +/* Deals with size <= 32. */ + .align 4 +L(small_range): + cmplwi r4,0 + beq L(zero) + + 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. */ + slw r10,r10,r6 + srw r10,r10,r6 + cmplwi cr7,r10,0 + bne cr7,L(done) + + addi r9,r8,4 + cmplw r9,r7 + bge L(end_max) + b L(loop_small) + + .p2align 5 +L(loop_small): + lwzu r12,4(r8) + cmpb r10,r12,r0 + addi r9,r8,4 + cmplwi cr6,r10,0 + bne cr6,L(done) + cmplw r9,r7 + bge L(end_max) + b L(loop_small) +END (BP_SYM (__strnlen)) +weak_alias (BP_SYM (__strnlen), BP_SYM(strnlen)) +libc_hidden_builtin_def (strnlen) |