source: trunk/libs/newlib/src/newlib/libc/machine/xscale/memcmp.c @ 444

#if defined __thumb__

#include "../../string/memcmp.c"

#else

#include <string.h>
#include "xscale.h"

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