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https://github.com/autc04/Retro68.git
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90 lines
1.6 KiB
C
90 lines
1.6 KiB
C
#if defined __thumb__
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#include "../../string/memset.c"
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#else
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#include <string.h>
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#include "xscale.h"
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void *
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memset (void *dst, int c, size_t len)
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{
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int dummy;
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asm volatile ("tst %0, #0x3"
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#ifndef __OPTIMIZE_SIZE__
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"\n\
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beq 1f\n\
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b 2f\n\
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0:\n\
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strb %1, [%0], #1\n\
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tst %0, #0x3\n\
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beq 1f\n\
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2:\n\
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movs r3, %2\n\
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sub %2, %2, #1\n\
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bne 0b\n\
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# At this point we know that %2 == len == -1 (since the SUB has already taken\n\
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# place). If we fall through to the 1: label (as the code used to do), the\n\
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# CMP will detect this negative value and branch to the 2: label. This will\n\
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# test %2 again, but this time against 0. The test will fail and the loop\n\
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# at 2: will go on for (almost) ever. Hence the explicit branch to the end\n\
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# of the hand written assembly code.\n\
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b 4f\n\
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1:\n\
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cmp %2, #0x3\n\
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bls 2f\n\
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and %1, %1, #0xff\n\
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orr lr, %1, %1, asl #8\n\
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cmp %2, #0xf\n\
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orr lr, lr, lr, asl #16\n\
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bls 1f\n\
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mov r3, lr\n\
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mov r4, lr\n\
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mov r5, lr\n\
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0:\n\
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sub %2, %2, #16\n\
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stmia %0!, { r3, r4, r5, lr }\n\
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cmp %2, #0xf\n\
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bhi 0b\n\
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1:\n\
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cmp %2, #0x7\n\
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bls 1f\n\
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mov r3, lr\n\
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0:\n\
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sub %2, %2, #8\n\
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stmia %0!, { r3, lr }\n\
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cmp %2, #0x7\n\
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bhi 0b\n\
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1:\n\
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cmp %2, #0x3\n\
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bls 2f\n\
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0:\n\
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sub %2, %2, #4\n\
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str lr, [%0], #4\n\
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cmp %2, #0x3\n\
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bhi 0b\n\
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"
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#endif /* !__OPTIMIZE_SIZE__ */
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"\n\
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2:\n\
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movs r3, %2\n\
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sub %2, %2, #1\n\
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beq 4f\n\
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0:\n\
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movs r3, %2\n\
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sub %2, %2, #1\n\
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strb %1, [%0], #1\n\
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bne 0b\n\
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4:"
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: "=&r" (dummy), "=&r" (c), "=&r" (len)
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: "0" (dst), "1" (c), "2" (len)
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: "memory", "r3", "r4", "r5", "lr");
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return dst;
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}
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#endif
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