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jeremybenn |
#if defined __thumb__
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#include "../../string/memcmp.c"
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#else
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#include <string.h>
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#include "xscale.h"
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int
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memcmp (const void * s1, const void * s2, size_t len)
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{
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int result;
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asm (
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#ifndef __OPTIMIZE_SIZE__
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"\n\
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cmp %2, #0x3 @ Is the length a multiple of four ?\n\
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bls 6f @ no = goto SLOW CHECK\n\
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and r2, %0, #0x3 @ get alignment of first pointer\n\
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and r3, %1, #0x3 @ get alignment of second pointer\n\
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cmp r2, r3 @ Do the two pointers share the same alignment ?\n\
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bne 6f @ no = goto SLOW CHECK\n\
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mov lr, %0 @ copy first pointer into LR\n\
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mov r4, %1 @ copy second pointer into R4\n\
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cmp r2, #0x0 @ Are we comparing word aligned pointers ?\n\
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beq 3f @ yes = goto START WORD CHECK LOOP\n\
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b 1f @ jump to LOOP TEST\n\
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0: @ LOOP START\n\
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ldrb r2, [lr], #1 @ load byte from LR, post inc.\n\
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" PRELOADSTR("lr") " @ preload\n\
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ldrb r3, [r4], #1 @ load byte from R4, post inc.\n\
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" PRELOADSTR("r4") " @ preload\n\
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cmp r2, r3 @ are the two bytes the same ?\n\
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bne 5f @ no = goto EXIT\n\
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tst lr, #0x3 @ has the LR become word aligned ?\n\
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bne 1f @ no = skip the next test\n\
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cmp %2, #4 @ is the count >= 4 ?\n\
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bhs 3f @ yes = goto START WORD CHECK LOOP\n\
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1: @ LOOP TEST\n\
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sub %2, %2, #1 @ decrement count by one\n\
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cmn %2, #0x1 @ has the count reached -1 ?\n\
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bne 0b @ no = loop back to LOOP START\n\
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b 4f @ goto PASS END\n\
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\n\
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0: @ ??\n\
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cmp %2, #0x7 @ Is the count a multiple of 8 ?\n\
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bls 3f @ no = goto ???\n\
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ldmia lr,{r2, r3} @ get two words from first pointer, post inc\n\
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ldmia r4,{r5, r6} @ get two words from second pointer, post inc\n\
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sub %2, %2, #0x4 @ decrement count by 4\n\
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cmp r2, r5 @ has the count reached ????\n\
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bne 1f @ no = goto\n\
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sub %2, %2, #0x4 @ decrement the count by 4\n\
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add lr, lr, #0x4 @ add 4 to first pointer\n\
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add r4, r4, #0x4 @ add 4 to second pointer\n\
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cmp r3, r6 @ ???\n\
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beq 0b @ goto ???\n\
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1: @ ??\n\
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add %2, %2, #0x4 @ Add four to count\n\
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sub %0, lr, #0x4 @ decrement first pointer by 4\n\
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sub %1, r4, #0x4 @ decrement second pointer by 4\n\
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b 6f @ goto SLOW CHECK\n\
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\n\
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3: @ START WORD CHECK LOOP\n\
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cmp %2, #0x3 @ is the count <= 3 ?\n\
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bls 1f @ yes = goto CHECK BYTES BY HAND\n\
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ldr r2, [lr], #4 @ get word from LR, post inc\n\
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ldr r3, [r4], #4 @ get word from R4, post inc\n\
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sub %2, %2, #4 @ decrement count by 4\n\
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cmp r2, r3 @ are the two words the same ?\n\
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bne 1f @ no = goto CHECK WORD CONTENTS\n\
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0: @ WORD CHECK LOOP\n\
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cmp %2, #0x3 @ is the count <= 3 ?\n\
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bls 1f @ yes = goto CHECK BYTES BY HAND\n\
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ldr r2, [lr], #4 @ load word from LR, post inc\n\
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" PRELOADSTR("lr") " @ preload\n\
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ldr r3, [r4], #4 @ load word from R4, post inc\n\
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" PRELOADSTR("r4") " @ preload\n\
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sub %2, %2, #4 @ decrement count by 4\n\
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cmp r2, r3 @ are the two words the same ?\n\
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beq 0b @ yes = goto WORD CHECK LOOP\n\
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1: @ CHECK BYTES BY HAND\n\
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sub %0, lr, #0x4 @ move LR back a word and put into first pointer\n\
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sub %1, r4, #0x4 @ move R4 back a word and put into second pointer\n\
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add %2, %2, #4 @ increment the count by 4\n\
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@ fall through into SLOW CHECK"
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#endif /* !__OPTIMIZE_SIZE__ */
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"\n\
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6: @ SLOW CHECK\n\
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sub %2, %2, #1 @ Decrement the count by one\n\
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cmn %2, #0x1 @ Has the count reached -1 ?\n\
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beq 4f @ Yes - we are finished, goto PASS END\n\
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0: @ LOOP1\n\
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ldrb r2, [%0], #1 @ get byte from first pointer\n\
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" PRELOADSTR("%0") " @ preload first pointer\n\
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ldrb r3, [%1], #1 @ get byte from second pointer\n\
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" PRELOADSTR("%1") " @ preload second pointer\n\
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cmp r2, r3 @ compare the two loaded bytes\n\
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bne 5f @ if they are not equal goto EXIT\n\
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sub %2, %2, #1 @ decremented count by 1\n\
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cmn %2, #0x1 @ has the count reached -1 ?\n\
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bne 0b @ no = then go back to LOOP1\n\
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4: @ PASS END\n\
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mov r3, r2 @ Default return value is 0\n\
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5: @ EXIT\n\
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rsb %0, r3, r2 @ return difference between last two bytes loaded"
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: "=r" (result), "=&r" (s2), "=&r" (len)
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: "0" (s1), "1" (s2), "2" (len)
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: "r2", "r3", "r4", "r5", "r6", "cc", "lr");
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return result;
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}
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#endif
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