| // Copyright 2018 The Go Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style |
| // license that can be found in the LICENSE file. |
| |
| #include "go_asm.h" |
| #include "textflag.h" |
| |
| TEXT ·Compare(SB),NOSPLIT,$0-28 |
| MOVL a_base+0(FP), SI |
| MOVL a_len+4(FP), BX |
| MOVL b_base+12(FP), DI |
| MOVL b_len+16(FP), DX |
| LEAL ret+24(FP), AX |
| JMP cmpbody<>(SB) |
| |
| TEXT runtime·cmpstring(SB),NOSPLIT,$0-20 |
| MOVL a_base+0(FP), SI |
| MOVL a_len+4(FP), BX |
| MOVL b_base+8(FP), DI |
| MOVL b_len+12(FP), DX |
| LEAL ret+16(FP), AX |
| JMP cmpbody<>(SB) |
| |
| // input: |
| // SI = a |
| // DI = b |
| // BX = alen |
| // DX = blen |
| // AX = address of return word (set to 1/0/-1) |
| TEXT cmpbody<>(SB),NOSPLIT,$0-0 |
| MOVL DX, BP |
| SUBL BX, DX // DX = blen-alen |
| JLE 2(PC) |
| MOVL BX, BP // BP = min(alen, blen) |
| CMPL SI, DI |
| JEQ allsame |
| CMPL BP, $4 |
| JB small |
| CMPB internal∕cpu·X86+const_offsetX86HasSSE2(SB), $1 |
| JNE mediumloop |
| largeloop: |
| CMPL BP, $16 |
| JB mediumloop |
| MOVOU (SI), X0 |
| MOVOU (DI), X1 |
| PCMPEQB X0, X1 |
| PMOVMSKB X1, BX |
| XORL $0xffff, BX // convert EQ to NE |
| JNE diff16 // branch if at least one byte is not equal |
| ADDL $16, SI |
| ADDL $16, DI |
| SUBL $16, BP |
| JMP largeloop |
| |
| diff16: |
| BSFL BX, BX // index of first byte that differs |
| XORL DX, DX |
| MOVB (SI)(BX*1), CX |
| CMPB CX, (DI)(BX*1) |
| SETHI DX |
| LEAL -1(DX*2), DX // convert 1/0 to +1/-1 |
| MOVL DX, (AX) |
| RET |
| |
| mediumloop: |
| CMPL BP, $4 |
| JBE _0through4 |
| MOVL (SI), BX |
| MOVL (DI), CX |
| CMPL BX, CX |
| JNE diff4 |
| ADDL $4, SI |
| ADDL $4, DI |
| SUBL $4, BP |
| JMP mediumloop |
| |
| _0through4: |
| MOVL -4(SI)(BP*1), BX |
| MOVL -4(DI)(BP*1), CX |
| CMPL BX, CX |
| JEQ allsame |
| |
| diff4: |
| BSWAPL BX // reverse order of bytes |
| BSWAPL CX |
| XORL BX, CX // find bit differences |
| BSRL CX, CX // index of highest bit difference |
| SHRL CX, BX // move a's bit to bottom |
| ANDL $1, BX // mask bit |
| LEAL -1(BX*2), BX // 1/0 => +1/-1 |
| MOVL BX, (AX) |
| RET |
| |
| // 0-3 bytes in common |
| small: |
| LEAL (BP*8), CX |
| NEGL CX |
| JEQ allsame |
| |
| // load si |
| CMPB SI, $0xfc |
| JA si_high |
| MOVL (SI), SI |
| JMP si_finish |
| si_high: |
| MOVL -4(SI)(BP*1), SI |
| SHRL CX, SI |
| si_finish: |
| SHLL CX, SI |
| |
| // same for di |
| CMPB DI, $0xfc |
| JA di_high |
| MOVL (DI), DI |
| JMP di_finish |
| di_high: |
| MOVL -4(DI)(BP*1), DI |
| SHRL CX, DI |
| di_finish: |
| SHLL CX, DI |
| |
| BSWAPL SI // reverse order of bytes |
| BSWAPL DI |
| XORL SI, DI // find bit differences |
| JEQ allsame |
| BSRL DI, CX // index of highest bit difference |
| SHRL CX, SI // move a's bit to bottom |
| ANDL $1, SI // mask bit |
| LEAL -1(SI*2), BX // 1/0 => +1/-1 |
| MOVL BX, (AX) |
| RET |
| |
| // all the bytes in common are the same, so we just need |
| // to compare the lengths. |
| allsame: |
| XORL BX, BX |
| XORL CX, CX |
| TESTL DX, DX |
| SETLT BX // 1 if alen > blen |
| SETEQ CX // 1 if alen == blen |
| LEAL -1(CX)(BX*2), BX // 1,0,-1 result |
| MOVL BX, (AX) |
| RET |
