// 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
#ifdef GO386_softfloat
JMP mediumloop
#endif
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
