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Diffstat (limited to 'sysdeps/arm/armv6/strrchr.S')
| -rw-r--r-- | sysdeps/arm/armv6/strrchr.S | 131 |
1 files changed, 131 insertions, 0 deletions
diff --git a/sysdeps/arm/armv6/strrchr.S b/sysdeps/arm/armv6/strrchr.S new file mode 100644 index 0000000000..a1e753c11b --- /dev/null +++ b/sysdeps/arm/armv6/strrchr.S @@ -0,0 +1,131 @@ +/* strrchr -- find the last occurence of C in a nul-terminated string + Copyright (C) 2013-2014 Free Software Foundation, Inc. + 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> + + .syntax unified + .text + +ENTRY (strrchr) + @ r0 = start of string + @ r1 = character to match + @ returns NULL for no match, or a pointer to the match + + mov r3, r0 + mov r0, #0 + uxtb r1, r1 + + @ Loop a few times until we're aligned. + tst r3, #7 + beq 2f +1: sfi_breg r3, \ + ldrb r2, [\B], #1 + cmp r2, r1 @ Find the character + it eq + subeq r0, r3, #1 + cmp r2, #0 @ Find EOS + it eq + bxeq lr + tst r3, #7 @ Find the aligment point + bne 1b + + @ So now we're aligned. Now we actually need a stack frame. +2: push { r4, r5, r6, r7 } + cfi_adjust_cfa_offset (16) + cfi_rel_offset (r4, 0) + cfi_rel_offset (r5, 4) + cfi_rel_offset (r6, 8) + cfi_rel_offset (r7, 12) + + orr r1, r1, r1, lsl #8 @ Replicate C to all bytes +#ifdef ARCH_HAS_T2 + movw ip, #0x0101 + movt ip, #0x0101 +#else + ldr ip, =0x01010101 +#endif + orr r1, r1, r1, lsl #16 + mov r2, #0 @ No found bits yet + + @ Loop searching for EOS and C, 8 bytes at a time. + @ Any time we find a match in a word, we copy the address of + @ the word to r0, and the found bits to r2. +3: sfi_breg r3, \ + ldrd r4, r5, [\B], #8 + @ Subtracting (unsigned saturating) from 1 means result of 1 for + @ any byte that was originally zero and 0 otherwise. Therefore + @ we consider the lsb of each byte the "found" bit. + uqsub8 r6, ip, r4 @ Find EOS + uqsub8 r7, ip, r5 + eor r4, r4, r1 @ Convert C bytes to 0 + eor r5, r5, r1 + uqsub8 r4, ip, r4 @ Find C + uqsub8 r5, ip, r5 + cmp r6, #0 @ Found EOS, first word + bne 4f + cmp r4, #0 @ Handle C, first word + itt ne + subne r0, r3, #8 + movne r2, r4 + cmp r7, #0 @ Found EOS, second word + bne 5f + cmp r5, #0 @ Handle C, second word + itt ne + subne r0, r3, #4 + movne r2, r5 + b 3b + + @ Found EOS in second word; fold to first word. +5: add r3, r3, #4 @ Dec pointer to 2nd word, with below + mov r4, r5 @ Overwrite first word C found + mov r6, r7 @ Overwrite first word EOS found + + @ Found EOS. Zap found C after EOS. +4: sub r3, r3, #8 @ Decrement pointer to first word +#ifdef __ARMEB__ + @ Byte swap to be congruent with LE, which is easier from here on. + rev r6, r6 @ Byte swap found EOS, + rev r4, r4 @ ... this found C + rev r2, r2 @ ... prev found C +#endif + sub r7, r6, #1 @ Toggle EOS lsb and below + eor r6, r6, r7 @ All bits below and including lsb + ands r4, r4, r6 @ Zap C above EOS + itt ne + movne r2, r4 @ Copy to result, if still non-zero + movne r0, r3 + + pop { r4, r5, r6, r7 } + cfi_adjust_cfa_offset (-16) + cfi_restore (r4) + cfi_restore (r5) + cfi_restore (r6) + cfi_restore (r7) + + @ Adjust the result pointer if we found a word containing C. + cmp r2, #0 + clz r2, r2 @ Find the bit offset of the last C + itt ne + rsbne r2, r2, #32 @ Convert to a count from the right + addne r0, r0, r2, lsr #3 @ Convert to byte offset and add. + bx lr + +END (strrchr) + +weak_alias (strrchr, rindex) +libc_hidden_builtin_def (strrchr) |