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Diffstat (limited to 'src/string/armel/memcpy.s')
| -rw-r--r-- | src/string/armel/memcpy.s | 381 |
1 files changed, 381 insertions, 0 deletions
diff --git a/src/string/armel/memcpy.s b/src/string/armel/memcpy.s new file mode 100644 index 00000000..9f24a4f3 --- /dev/null +++ b/src/string/armel/memcpy.s @@ -0,0 +1,381 @@ +/* + * 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. + */ + + +/* + * Optimized memcpy() for ARM. + * + * note that memcpy() always returns the destination pointer, + * so we have to preserve R0. + */ + +/* + * This file has been modified from the original for use in musl libc. + * The main changes are: addition of .type memcpy,%function to make the + * code safely callable from thumb mode, adjusting the return + * instructions to be compatible with pre-thumb ARM cpus, and removal + * of prefetch code that is not compatible with older cpus. + */ + +.global memcpy +.type memcpy,%function +memcpy: + /* The stack must always be 64-bits aligned to be compliant with the + * ARM ABI. Since we have to save R0, we might as well save R4 + * which we can use for better pipelining of the reads below + */ + .fnstart + .save {r0, r4, lr} + stmfd sp!, {r0, r4, lr} + /* Making room for r5-r11 which will be spilled later */ + .pad #28 + sub sp, sp, #28 + + /* it simplifies things to take care of len<4 early */ + cmp r2, #4 + blo copy_last_3_and_return + + /* compute the offset to align the source + * offset = (4-(src&3))&3 = -src & 3 + */ + rsb r3, r1, #0 + ands r3, r3, #3 + beq src_aligned + + /* align source to 32 bits. We need to insert 2 instructions between + * a ldr[b|h] and str[b|h] because byte and half-word instructions + * stall 2 cycles. + */ + movs r12, r3, lsl #31 + sub r2, r2, r3 /* we know that r3 <= r2 because r2 >= 4 */ + ldrmib r3, [r1], #1 + ldrcsb r4, [r1], #1 + ldrcsb r12,[r1], #1 + strmib r3, [r0], #1 + strcsb r4, [r0], #1 + strcsb r12,[r0], #1 + +src_aligned: + + /* see if src and dst are aligned together (congruent) */ + eor r12, r0, r1 + tst r12, #3 + bne non_congruent + + /* Use post-incriment mode for stm to spill r5-r11 to reserved stack + * frame. Don't update sp. + */ + stmea sp, {r5-r11} + + /* align the destination to a cache-line */ + rsb r3, r0, #0 + ands r3, r3, #0x1C + beq congruent_aligned32 + cmp r3, r2 + andhi r3, r2, #0x1C + + /* conditionnaly copies 0 to 7 words (length in r3) */ + movs r12, r3, lsl #28 + ldmcsia r1!, {r4, r5, r6, r7} /* 16 bytes */ + ldmmiia r1!, {r8, r9} /* 8 bytes */ + stmcsia r0!, {r4, r5, r6, r7} + stmmiia r0!, {r8, r9} + tst r3, #0x4 + ldrne r10,[r1], #4 /* 4 bytes */ + strne r10,[r0], #4 + sub r2, r2, r3 + +congruent_aligned32: + /* + * here source is aligned to 32 bytes. + */ + +cached_aligned32: + subs r2, r2, #32 + blo less_than_32_left + + /* + * We preload a cache-line up to 64 bytes ahead. On the 926, this will + * stall only until the requested world is fetched, but the linefill + * continues in the the background. + * While the linefill is going, we write our previous cache-line + * into the write-buffer (which should have some free space). + * When the linefill is done, the writebuffer will + * start dumping its content into memory + * + * While all this is going, we then load a full cache line into + * 8 registers, this cache line should be in the cache by now + * (or partly in the cache). + * + * This code should work well regardless of the source/dest alignment. + * + */ + + /* Align the preload register to a cache-line because the cpu does + * "critical word first" (the first word requested is loaded first). + */ + @ bic r12, r1, #0x1F + @ add r12, r12, #64 + +1: ldmia r1!, { r4-r11 } + subs r2, r2, #32 + + /* + * NOTE: if r12 is more than 64 ahead of r1, the following ldrhi + * for ARM9 preload will not be safely guarded by the preceding subs. + * When it is safely guarded the only possibility to have SIGSEGV here + * is because the caller overstates the length. + */ + @ ldrhi r3, [r12], #32 /* cheap ARM9 preload */ + stmia r0!, { r4-r11 } + bhs 1b + + add r2, r2, #32 + +less_than_32_left: + /* + * less than 32 bytes left at this point (length in r2) + */ + + /* skip all this if there is nothing to do, which should + * be a common case (if not executed the code below takes + * about 16 cycles) + */ + tst r2, #0x1F + beq 1f + + /* conditionnaly copies 0 to 31 bytes */ + movs r12, r2, lsl #28 + ldmcsia r1!, {r4, r5, r6, r7} /* 16 bytes */ + ldmmiia r1!, {r8, r9} /* 8 bytes */ + stmcsia r0!, {r4, r5, r6, r7} + stmmiia r0!, {r8, r9} + movs r12, r2, lsl #30 + ldrcs r3, [r1], #4 /* 4 bytes */ + ldrmih r4, [r1], #2 /* 2 bytes */ + strcs r3, [r0], #4 + strmih r4, [r0], #2 + tst r2, #0x1 + ldrneb r3, [r1] /* last byte */ + strneb r3, [r0] + + /* we're done! restore everything and return */ +1: ldmfd sp!, {r5-r11} + ldmfd sp!, {r0, r4, lr} + tst lr, #1 + moveq pc, lr + bx lr + + /********************************************************************/ + +non_congruent: + /* + * here source is aligned to 4 bytes + * but destination is not. + * + * in the code below r2 is the number of bytes read + * (the number of bytes written is always smaller, because we have + * partial words in the shift queue) + */ + cmp r2, #4 + blo copy_last_3_and_return + + /* Use post-incriment mode for stm to spill r5-r11 to reserved stack + * frame. Don't update sp. + */ + stmea sp, {r5-r11} + + /* compute shifts needed to align src to dest */ + rsb r5, r0, #0 + and r5, r5, #3 /* r5 = # bytes in partial words */ + mov r12, r5, lsl #3 /* r12 = right */ + rsb lr, r12, #32 /* lr = left */ + + /* read the first word */ + ldr r3, [r1], #4 + sub r2, r2, #4 + + /* write a partial word (0 to 3 bytes), such that destination + * becomes aligned to 32 bits (r5 = nb of words to copy for alignment) + */ + movs r5, r5, lsl #31 + strmib r3, [r0], #1 + movmi r3, r3, lsr #8 + strcsb r3, [r0], #1 + movcs r3, r3, lsr #8 + strcsb r3, [r0], #1 + movcs r3, r3, lsr #8 + + cmp r2, #4 + blo partial_word_tail + + /* Align destination to 32 bytes (cache line boundary) */ +1: tst r0, #0x1c + beq 2f + ldr r5, [r1], #4 + sub r2, r2, #4 + orr r4, r3, r5, lsl lr + mov r3, r5, lsr r12 + str r4, [r0], #4 + cmp r2, #4 + bhs 1b + blo partial_word_tail + + /* copy 32 bytes at a time */ +2: subs r2, r2, #32 + blo less_than_thirtytwo + + /* Use immediate mode for the shifts, because there is an extra cycle + * for register shifts, which could account for up to 50% of + * performance hit. + */ + + cmp r12, #24 + beq loop24 + cmp r12, #8 + beq loop8 + +loop16: + ldr r12, [r1], #4 +1: mov r4, r12 + ldmia r1!, { r5,r6,r7, r8,r9,r10,r11} + subs r2, r2, #32 + ldrhs r12, [r1], #4 + orr r3, r3, r4, lsl #16 + mov r4, r4, lsr #16 + orr r4, r4, r5, lsl #16 + mov r5, r5, lsr #16 + orr r5, r5, r6, lsl #16 + mov r6, r6, lsr #16 + orr r6, r6, r7, lsl #16 + mov r7, r7, lsr #16 + orr r7, r7, r8, lsl #16 + mov r8, r8, lsr #16 + orr r8, r8, r9, lsl #16 + mov r9, r9, lsr #16 + orr r9, r9, r10, lsl #16 + mov r10, r10, lsr #16 + orr r10, r10, r11, lsl #16 + stmia r0!, {r3,r4,r5,r6, r7,r8,r9,r10} + mov r3, r11, lsr #16 + bhs 1b + b less_than_thirtytwo + +loop8: + ldr r12, [r1], #4 +1: mov r4, r12 + ldmia r1!, { r5,r6,r7, r8,r9,r10,r11} + subs r2, r2, #32 + ldrhs r12, [r1], #4 + orr r3, r3, r4, lsl #24 + mov r4, r4, lsr #8 + orr r4, r4, r5, lsl #24 + mov r5, r5, lsr #8 + orr r5, r5, r6, lsl #24 + mov r6, r6, lsr #8 + orr r6, r6, r7, lsl #24 + mov r7, r7, lsr #8 + orr r7, r7, r8, lsl #24 + mov r8, r8, lsr #8 + orr r8, r8, r9, lsl #24 + mov r9, r9, lsr #8 + orr r9, r9, r10, lsl #24 + mov r10, r10, lsr #8 + orr r10, r10, r11, lsl #24 + stmia r0!, {r3,r4,r5,r6, r7,r8,r9,r10} + mov r3, r11, lsr #8 + bhs 1b + b less_than_thirtytwo + +loop24: + ldr r12, [r1], #4 +1: mov r4, r12 + ldmia r1!, { r5,r6,r7, r8,r9,r10,r11} + subs r2, r2, #32 + ldrhs r12, [r1], #4 + orr r3, r3, r4, lsl #8 + mov r4, r4, lsr #24 + orr r4, r4, r5, lsl #8 + mov r5, r5, lsr #24 + orr r5, r5, r6, lsl #8 + mov r6, r6, lsr #24 + orr r6, r6, r7, lsl #8 + mov r7, r7, lsr #24 + orr r7, r7, r8, lsl #8 + mov r8, r8, lsr #24 + orr r8, r8, r9, lsl #8 + mov r9, r9, lsr #24 + orr r9, r9, r10, lsl #8 + mov r10, r10, lsr #24 + orr r10, r10, r11, lsl #8 + stmia r0!, {r3,r4,r5,r6, r7,r8,r9,r10} + mov r3, r11, lsr #24 + bhs 1b + +less_than_thirtytwo: + /* copy the last 0 to 31 bytes of the source */ + rsb r12, lr, #32 /* we corrupted r12, recompute it */ + add r2, r2, #32 + cmp r2, #4 + blo partial_word_tail + +1: ldr r5, [r1], #4 + sub r2, r2, #4 + orr r4, r3, r5, lsl lr + mov r3, r5, lsr r12 + str r4, [r0], #4 + cmp r2, #4 + bhs 1b + +partial_word_tail: + /* we have a partial word in the input buffer */ + movs r5, lr, lsl #(31-3) + strmib r3, [r0], #1 + movmi r3, r3, lsr #8 + strcsb r3, [r0], #1 + movcs r3, r3, lsr #8 + strcsb r3, [r0], #1 + + /* Refill spilled registers from the stack. Don't update sp. */ + ldmfd sp, {r5-r11} + +copy_last_3_and_return: + movs r2, r2, lsl #31 /* copy remaining 0, 1, 2 or 3 bytes */ + ldrmib r2, [r1], #1 + ldrcsb r3, [r1], #1 + ldrcsb r12,[r1] + strmib r2, [r0], #1 + strcsb r3, [r0], #1 + strcsb r12,[r0] + + /* we're done! restore sp and spilled registers and return */ + add sp, sp, #28 + ldmfd sp!, {r0, r4, lr} + tst lr, #1 + moveq pc, lr + bx lr |