mirror of https://github.com/golang/go.git
152 lines
2.8 KiB
ArmAsm
152 lines
2.8 KiB
ArmAsm
// Copyright 2018 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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#include "go_asm.h"
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#include "textflag.h"
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TEXT ·Compare(SB),NOSPLIT,$0-28
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MOVL a_base+0(FP), SI
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MOVL a_len+4(FP), BX
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MOVL b_base+12(FP), DI
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MOVL b_len+16(FP), DX
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LEAL ret+24(FP), AX
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JMP cmpbody<>(SB)
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TEXT bytes·Compare(SB),NOSPLIT,$0-28
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MOVL a_base+0(FP), SI
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MOVL a_len+4(FP), BX
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MOVL b_base+12(FP), DI
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MOVL b_len+16(FP), DX
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LEAL ret+24(FP), AX
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JMP cmpbody<>(SB)
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TEXT runtime·cmpstring(SB),NOSPLIT,$0-20
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MOVL a_base+0(FP), SI
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MOVL a_len+4(FP), BX
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MOVL b_base+8(FP), DI
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MOVL b_len+12(FP), DX
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LEAL ret+16(FP), AX
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JMP cmpbody<>(SB)
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// input:
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// SI = a
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// DI = b
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// BX = alen
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// DX = blen
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// AX = address of return word (set to 1/0/-1)
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TEXT cmpbody<>(SB),NOSPLIT,$0-0
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MOVL DX, BP
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SUBL BX, DX // DX = blen-alen
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JLE 2(PC)
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MOVL BX, BP // BP = min(alen, blen)
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CMPL SI, DI
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JEQ allsame
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CMPL BP, $4
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JB small
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CMPB runtime·support_sse2(SB), $1
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JNE mediumloop
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largeloop:
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CMPL BP, $16
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JB mediumloop
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MOVOU (SI), X0
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MOVOU (DI), X1
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PCMPEQB X0, X1
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PMOVMSKB X1, BX
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XORL $0xffff, BX // convert EQ to NE
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JNE diff16 // branch if at least one byte is not equal
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ADDL $16, SI
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ADDL $16, DI
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SUBL $16, BP
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JMP largeloop
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diff16:
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BSFL BX, BX // index of first byte that differs
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XORL DX, DX
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MOVB (SI)(BX*1), CX
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CMPB CX, (DI)(BX*1)
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SETHI DX
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LEAL -1(DX*2), DX // convert 1/0 to +1/-1
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MOVL DX, (AX)
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RET
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mediumloop:
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CMPL BP, $4
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JBE _0through4
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MOVL (SI), BX
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MOVL (DI), CX
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CMPL BX, CX
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JNE diff4
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ADDL $4, SI
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ADDL $4, DI
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SUBL $4, BP
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JMP mediumloop
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_0through4:
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MOVL -4(SI)(BP*1), BX
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MOVL -4(DI)(BP*1), CX
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CMPL BX, CX
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JEQ allsame
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diff4:
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BSWAPL BX // reverse order of bytes
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BSWAPL CX
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XORL BX, CX // find bit differences
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BSRL CX, CX // index of highest bit difference
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SHRL CX, BX // move a's bit to bottom
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ANDL $1, BX // mask bit
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LEAL -1(BX*2), BX // 1/0 => +1/-1
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MOVL BX, (AX)
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RET
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// 0-3 bytes in common
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small:
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LEAL (BP*8), CX
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NEGL CX
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JEQ allsame
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// load si
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CMPB SI, $0xfc
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JA si_high
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MOVL (SI), SI
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JMP si_finish
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si_high:
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MOVL -4(SI)(BP*1), SI
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SHRL CX, SI
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si_finish:
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SHLL CX, SI
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// same for di
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CMPB DI, $0xfc
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JA di_high
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MOVL (DI), DI
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JMP di_finish
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di_high:
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MOVL -4(DI)(BP*1), DI
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SHRL CX, DI
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di_finish:
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SHLL CX, DI
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BSWAPL SI // reverse order of bytes
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BSWAPL DI
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XORL SI, DI // find bit differences
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JEQ allsame
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BSRL DI, CX // index of highest bit difference
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SHRL CX, SI // move a's bit to bottom
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ANDL $1, SI // mask bit
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LEAL -1(SI*2), BX // 1/0 => +1/-1
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MOVL BX, (AX)
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RET
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// all the bytes in common are the same, so we just need
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// to compare the lengths.
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allsame:
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XORL BX, BX
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XORL CX, CX
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TESTL DX, DX
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SETLT BX // 1 if alen > blen
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SETEQ CX // 1 if alen == blen
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LEAL -1(CX)(BX*2), BX // 1,0,-1 result
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MOVL BX, (AX)
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RET
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