| /* |
| * Copyright (C) 2008 The Android Open Source Project |
| * All rights reserved. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions |
| * are met: |
| * * Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * * Redistributions in binary form must reproduce the above copyright |
| * notice, this list of conditions and the following disclaimer in |
| * the documentation and/or other materials provided with the |
| * distribution. |
| * |
| * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
| * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
| * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS |
| * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE |
| * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, |
| * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, |
| * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS |
| * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED |
| * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, |
| * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT |
| * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
| * SUCH DAMAGE. |
| */ |
| |
| #include <machine/cpu-features.h> |
| #include <machine/asm.h> |
| |
| /* |
| * Optimized memcmp16() for ARM9. |
| * This would not be optimal on XScale or ARM11, where more prefetching |
| * and use of PLD will be needed. |
| * The 2 major optimzations here are |
| * (1) The main loop compares 16 bytes at a time |
| * (2) The loads are scheduled in a way they won't stall |
| */ |
| |
| ENTRY(__memcmp16) |
| PLD (r0, #0) |
| PLD (r1, #0) |
| |
| /* take of the case where length is nul or the buffers are the same */ |
| cmp r0, r1 |
| cmpne r2, #0 |
| moveq r0, #0 |
| bxeq lr |
| |
| /* since r0 hold the result, move the first source |
| * pointer somewhere else |
| */ |
| |
| mov r3, r0 |
| |
| /* make sure we have at least 12 words, this simplify things below |
| * and avoid some overhead for small blocks |
| */ |
| |
| cmp r2, #12 |
| bpl 0f |
| |
| /* small blocks (less then 12 words) */ |
| PLD (r0, #32) |
| PLD (r1, #32) |
| |
| 1: ldrh r0, [r3], #2 |
| ldrh ip, [r1], #2 |
| subs r0, r0, ip |
| bxne lr |
| subs r2, r2, #1 |
| bne 1b |
| bx lr |
| |
| |
| .save {r4, lr} |
| /* save registers */ |
| 0: stmfd sp!, {r4, lr} |
| |
| /* align first pointer to word boundary */ |
| tst r3, #2 |
| beq 0f |
| |
| ldrh r0, [r3], #2 |
| ldrh ip, [r1], #2 |
| sub r2, r2, #1 |
| subs r0, r0, ip |
| /* restore registers and return */ |
| ldmnefd sp!, {r4, lr} |
| bxne lr |
| |
| |
| 0: /* here the first pointer is aligned, and we have at least 3 words |
| * to process. |
| */ |
| |
| /* see if the pointers are congruent */ |
| eor r0, r3, r1 |
| ands r0, r0, #2 |
| bne 5f |
| |
| /* congruent case, 16 half-words per iteration |
| * We need to make sure there are at least 16+2 words left |
| * because we effectively read ahead one long word, and we could |
| * read past the buffer (and segfault) if we're not careful. |
| */ |
| |
| ldr ip, [r1] |
| subs r2, r2, #(16 + 2) |
| bmi 1f |
| |
| 0: |
| PLD (r3, #64) |
| PLD (r1, #64) |
| ldr r0, [r3], #4 |
| ldr lr, [r1, #4]! |
| eors r0, r0, ip |
| ldreq r0, [r3], #4 |
| ldreq ip, [r1, #4]! |
| eoreqs r0, r0, lr |
| ldreq r0, [r3], #4 |
| ldreq lr, [r1, #4]! |
| eoreqs r0, r0, ip |
| ldreq r0, [r3], #4 |
| ldreq ip, [r1, #4]! |
| eoreqs r0, r0, lr |
| ldreq r0, [r3], #4 |
| ldreq lr, [r1, #4]! |
| eoreqs r0, r0, ip |
| ldreq r0, [r3], #4 |
| ldreq ip, [r1, #4]! |
| eoreqs r0, r0, lr |
| ldreq r0, [r3], #4 |
| ldreq lr, [r1, #4]! |
| eoreqs r0, r0, ip |
| ldreq r0, [r3], #4 |
| ldreq ip, [r1, #4]! |
| eoreqs r0, r0, lr |
| bne 2f |
| subs r2, r2, #16 |
| bhs 0b |
| |
| /* do we have at least 2 words left? */ |
| 1: adds r2, r2, #(16 - 2 + 2) |
| bmi 4f |
| |
| /* finish off 2 words at a time */ |
| 3: ldr r0, [r3], #4 |
| ldr ip, [r1], #4 |
| eors r0, r0, ip |
| bne 2f |
| subs r2, r2, #2 |
| bhs 3b |
| |
| /* are we done? */ |
| 4: adds r2, r2, #2 |
| bne 8f |
| /* restore registers and return */ |
| mov r0, #0 |
| ldmfd sp!, {r4, lr} |
| bx lr |
| |
| 2: /* the last 2 words are different, restart them */ |
| ldrh r0, [r3, #-4] |
| ldrh ip, [r1, #-4] |
| subs r0, r0, ip |
| ldreqh r0, [r3, #-2] |
| ldreqh ip, [r1, #-2] |
| subeqs r0, r0, ip |
| /* restore registers and return */ |
| ldmfd sp!, {r4, lr} |
| bx lr |
| |
| /* process the last few words */ |
| 8: ldrh r0, [r3], #2 |
| ldrh ip, [r1], #2 |
| subs r0, r0, ip |
| bne 9f |
| subs r2, r2, #1 |
| bne 8b |
| |
| 9: /* restore registers and return */ |
| ldmfd sp!, {r4, lr} |
| bx lr |
| |
| |
| 5: /*************** non-congruent case ***************/ |
| |
| /* align the unaligned pointer */ |
| bic r1, r1, #3 |
| ldr lr, [r1], #4 |
| sub r2, r2, #8 |
| |
| 6: |
| PLD (r3, #64) |
| PLD (r1, #64) |
| mov ip, lr, lsr #16 |
| ldr lr, [r1], #4 |
| ldr r0, [r3], #4 |
| orr ip, ip, lr, lsl #16 |
| eors r0, r0, ip |
| moveq ip, lr, lsr #16 |
| ldreq lr, [r1], #4 |
| ldreq r0, [r3], #4 |
| orreq ip, ip, lr, lsl #16 |
| eoreqs r0, r0, ip |
| moveq ip, lr, lsr #16 |
| ldreq lr, [r1], #4 |
| ldreq r0, [r3], #4 |
| orreq ip, ip, lr, lsl #16 |
| eoreqs r0, r0, ip |
| moveq ip, lr, lsr #16 |
| ldreq lr, [r1], #4 |
| ldreq r0, [r3], #4 |
| orreq ip, ip, lr, lsl #16 |
| eoreqs r0, r0, ip |
| bne 7f |
| subs r2, r2, #8 |
| bhs 6b |
| sub r1, r1, #2 |
| /* are we done? */ |
| adds r2, r2, #8 |
| moveq r0, #0 |
| beq 9b |
| /* finish off the remaining bytes */ |
| b 8b |
| |
| 7: /* fix up the 2 pointers and fallthrough... */ |
| sub r1, r1, #2 |
| b 2b |
| END(__memcmp16) |
