ref: 11954a19a6252415c4eae086cc6b09bfbbc1aa9f
dir: /sys/src/libc/sparc/memcmp.s/
TEXT memcmp(SB), $0 /* * performance: * (tba) */ MOVW R7, 0(FP) MOVW n+8(FP), R9 /* R9 is count */ MOVW s1+0(FP), R10 /* R10 is pointer1 */ MOVW s2+4(FP), R11 /* R11 is pointer2 */ ADD R9,R10, R12 /* R12 is end pointer1 */ /* * if not at least 4 chars, * dont even mess around. * 3 chars to guarantee any * rounding up to a word * boundary and 4 characters * to get at least maybe one * full word cmp. */ SUBCC $4,R9, R0 BL out /* * test if both pointers * are similarly word alligned */ XOR R10,R11, R7 ANDCC $3,R7, R0 BNE out /* * byte at a time to word allign */ l1: ANDCC $3,R10, R0 BE l2 MOVBU 0(R10), R16 MOVBU 0(R11), R17 ADD $1, R10 SUBCC R16,R17, R0 BNE ne ADD $1, R11 JMP l1 /* * turn R9 into end pointer1-15 * cmp 16 at a time while theres room */ l2: SUB $15,R12, R9 l3: SUBCC R10,R9, R0 BLEU l4 MOVW 0(R10), R16 MOVW 0(R11), R17 MOVW 4(R10), R18 SUBCC R16,R17, R0 BNE ne MOVW 4(R11), R19 MOVW 8(R10), R16 SUBCC R18,R19, R0 BNE ne MOVW 8(R11), R17 MOVW 12(R10), R18 SUBCC R16,R17, R0 BNE ne MOVW 12(R11), R19 ADD $16, R10 SUBCC R18,R19, R0 BNE ne SUBCC R16,R17, R0 BNE ne ADD $16, R11 JMP l3 /* * turn R9 into end pointer1-3 * cmp 4 at a time while theres room */ l4: SUB $3,R12, R9 l5: SUBCC R10,R9, R0 BLEU out MOVW 0(R10), R16 MOVW 0(R11), R17 ADD $4, R10 SUBCC R16,R17, R0 /* only works because big endian */ BNE ne ADD $4, R11 JMP l5 /* * last loop, cmp byte at a time */ out: SUBCC R10,R12, R0 BE zero MOVBU 0(R10), R16 MOVBU 0(R11), R17 ADD $1, R10 SUBCC R16,R17, R0 BNE ne ADD $1, R11 JMP out ne: BGU plus MOVW $1, R7 RETURN plus: MOVW $-1, R7 RETURN zero: MOVW R0, R7 RETURN