ref: 464763202be7bdafa703c8c2ecfe1f4a5142f26f
dir: /sys/src/libc/mips/memcmp.s/
TEXT memcmp(SB), $0 MOVW R1, 0(FP) /* * performance: * alligned about 1.0us/call and 17.4mb/sec * unalligned is about 3.1mb/sec */ MOVW n+8(FP), R3 /* R3 is count */ MOVW s1+0(FP), R4 /* R4 is pointer1 */ MOVW s2+4(FP), R5 /* R5 is pointer2 */ ADDU R3,R4, R6 /* R6 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. */ SGT $4,R3, R1 BNE R1, out /* * test if both pointers * are similarly word alligned */ XOR R4,R5, R1 AND $3, R1 BNE R1, out /* * byte at a time to word allign */ l1: AND $3,R4, R1 BEQ R1, l2 MOVBU 0(R4), R8 MOVBU 0(R5), R9 ADDU $1, R4 BNE R8,R9, ne ADDU $1, R5 JMP l1 /* * turn R3 into end pointer1-15 * cmp 16 at a time while theres room */ l2: ADDU $-15,R6, R3 l3: SGTU R3,R4, R1 BEQ R1, l4 MOVW 0(R4), R8 MOVW 0(R5), R9 MOVW 4(R4), R10 BNE R8,R9, ne MOVW 4(R5), R11 MOVW 8(R4), R8 BNE R10,R11, ne1 MOVW 8(R5), R9 MOVW 12(R4), R10 BNE R8,R9, ne MOVW 12(R5), R11 ADDU $16, R4 BNE R10,R11, ne1 BNE R8,R9, ne ADDU $16, R5 JMP l3 /* * turn R3 into end pointer1-3 * cmp 4 at a time while theres room */ l4: ADDU $-3,R6, R3 l5: SGTU R3,R4, R1 BEQ R1, out MOVW 0(R4), R8 MOVW 0(R5), R9 ADDU $4, R4 BNE R8,R9, ne /* only works because big endian */ ADDU $4, R5 JMP l5 /* * last loop, cmp byte at a time */ out: SGTU R6,R4, R1 BEQ R1, ret MOVBU 0(R4), R8 MOVBU 0(R5), R9 ADDU $1, R4 BNE R8,R9, ne ADDU $1, R5 JMP out ne1: SGTU R10,R11, R1 BNE R1, ret MOVW $-1,R1 RET ne: SGTU R8,R9, R1 BNE R1, ret MOVW $-1,R1 ret: RET END