| /* Optimized strchr implementation for PowerPC. |
| Copyright (C) 1997-2014 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> |
| |
| /* See strlen.s for comments on how this works. */ |
| |
| /* char * [r3] strchr (const char *s [r3] , int c [r4] ) */ |
| |
| ENTRY (strchr) |
| |
| #define rTMP1 r0 |
| #define rRTN r3 /* outgoing result */ |
| #define rSTR r8 /* current word pointer */ |
| #define rCHR r4 /* byte we're looking for, spread over the whole word */ |
| #define rWORD r5 /* the current word */ |
| #define rCLZB rCHR /* leading zero byte count */ |
| #define rFEFE r6 /* constant 0xfefefeff (-0x01010101) */ |
| #define r7F7F r7 /* constant 0x7f7f7f7f */ |
| #define rTMP2 r9 |
| #define rIGN r10 /* number of bits we should ignore in the first word */ |
| #define rMASK r11 /* mask with the bits to ignore set to 0 */ |
| #define rTMP3 r12 |
| #define rTMP4 rIGN |
| #define rTMP5 rMASK |
| |
| |
| rlwimi rCHR, rCHR, 8, 16, 23 |
| li rMASK, -1 |
| rlwimi rCHR, rCHR, 16, 0, 15 |
| rlwinm rIGN, rRTN, 3, 27, 28 |
| lis rFEFE, -0x101 |
| lis r7F7F, 0x7f7f |
| clrrwi rSTR, rRTN, 2 |
| addi rFEFE, rFEFE, -0x101 |
| addi r7F7F, r7F7F, 0x7f7f |
| /* Test the first (partial?) word. */ |
| lwz rWORD, 0(rSTR) |
| #ifdef __LITTLE_ENDIAN__ |
| slw rMASK, rMASK, rIGN |
| #else |
| srw rMASK, rMASK, rIGN |
| #endif |
| orc rWORD, rWORD, rMASK |
| add rTMP1, rFEFE, rWORD |
| nor rTMP2, r7F7F, rWORD |
| and. rTMP4, rTMP1, rTMP2 |
| xor rTMP3, rCHR, rWORD |
| orc rTMP3, rTMP3, rMASK |
| b L(loopentry) |
| |
| /* The loop. */ |
| |
| L(loop): |
| lwzu rWORD, 4(rSTR) |
| and. rTMP5, rTMP1, rTMP2 |
| /* Test for 0. */ |
| add rTMP1, rFEFE, rWORD /* x - 0x01010101. */ |
| nor rTMP2, r7F7F, rWORD /* ~(x | 0x7f7f7f7f) == ~x & 0x80808080. */ |
| bne L(foundit) |
| and. rTMP4, rTMP1, rTMP2 /* (x - 0x01010101) & ~x & 0x80808080. */ |
| /* Start test for the bytes we're looking for. */ |
| xor rTMP3, rCHR, rWORD |
| L(loopentry): |
| add rTMP1, rFEFE, rTMP3 |
| nor rTMP2, r7F7F, rTMP3 |
| beq L(loop) |
| |
| /* There is a zero byte in the word, but may also be a matching byte (either |
| before or after the zero byte). In fact, we may be looking for a |
| zero byte, in which case we return a match. */ |
| and. rTMP5, rTMP1, rTMP2 |
| li rRTN, 0 |
| beqlr |
| /* At this point: |
| rTMP5 bytes are 0x80 for each match of c, 0 otherwise. |
| rTMP4 bytes are 0x80 for each match of 0, 0 otherwise. |
| But there may be false matches in the next most significant byte from |
| a true match due to carries. This means we need to recalculate the |
| matches using a longer method for big-endian. */ |
| #ifdef __LITTLE_ENDIAN__ |
| addi rTMP1, rTMP5, -1 |
| andc rTMP1, rTMP1, rTMP5 |
| cntlzw rCLZB, rTMP1 |
| addi rTMP2, rTMP4, -1 |
| andc rTMP2, rTMP2, rTMP4 |
| cmplw rTMP1, rTMP2 |
| bgtlr |
| subfic rCLZB, rCLZB, 32-7 |
| #else |
| /* I think we could reduce this by two instructions by keeping the "nor" |
| results from the loop for reuse here. See strlen.S tail. Similarly |
| one instruction could be pruned from L(foundit). */ |
| and rFEFE, r7F7F, rWORD |
| or rTMP5, r7F7F, rWORD |
| and rTMP1, r7F7F, rTMP3 |
| or rTMP4, r7F7F, rTMP3 |
| add rFEFE, rFEFE, r7F7F |
| add rTMP1, rTMP1, r7F7F |
| nor rWORD, rTMP5, rFEFE |
| nor rTMP2, rTMP4, rTMP1 |
| cntlzw rCLZB, rTMP2 |
| cmplw rWORD, rTMP2 |
| bgtlr |
| #endif |
| srwi rCLZB, rCLZB, 3 |
| add rRTN, rSTR, rCLZB |
| blr |
| |
| L(foundit): |
| #ifdef __LITTLE_ENDIAN__ |
| addi rTMP1, rTMP5, -1 |
| andc rTMP1, rTMP1, rTMP5 |
| cntlzw rCLZB, rTMP1 |
| subfic rCLZB, rCLZB, 32-7-32 |
| srawi rCLZB, rCLZB, 3 |
| #else |
| and rTMP1, r7F7F, rTMP3 |
| or rTMP4, r7F7F, rTMP3 |
| add rTMP1, rTMP1, r7F7F |
| nor rTMP2, rTMP4, rTMP1 |
| cntlzw rCLZB, rTMP2 |
| subi rSTR, rSTR, 4 |
| srwi rCLZB, rCLZB, 3 |
| #endif |
| add rRTN, rSTR, rCLZB |
| blr |
| END (strchr) |
| |
| weak_alias (strchr, index) |
| libc_hidden_builtin_def (strchr) |
