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69 lines
1.2 KiB
69 lines
1.2 KiB
// Copied from S2 implementation.
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//go:build !appengine && !noasm && gc && !noasm
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#include "textflag.h"
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// func matchLen(a []byte, b []byte) int
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// Requires: BMI
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TEXT ·matchLen(SB), NOSPLIT, $0-56
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MOVQ a_base+0(FP), AX
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MOVQ b_base+24(FP), CX
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MOVQ a_len+8(FP), DX
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// matchLen
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XORL SI, SI
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CMPL DX, $0x08
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JB matchlen_match4_standalone
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matchlen_loopback_standalone:
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MOVQ (AX)(SI*1), BX
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XORQ (CX)(SI*1), BX
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TESTQ BX, BX
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JZ matchlen_loop_standalone
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#ifdef GOAMD64_v3
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TZCNTQ BX, BX
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#else
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BSFQ BX, BX
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#endif
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SARQ $0x03, BX
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LEAL (SI)(BX*1), SI
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JMP gen_match_len_end
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matchlen_loop_standalone:
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LEAL -8(DX), DX
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LEAL 8(SI), SI
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CMPL DX, $0x08
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JAE matchlen_loopback_standalone
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matchlen_match4_standalone:
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CMPL DX, $0x04
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JB matchlen_match2_standalone
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MOVL (AX)(SI*1), BX
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CMPL (CX)(SI*1), BX
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JNE matchlen_match2_standalone
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LEAL -4(DX), DX
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LEAL 4(SI), SI
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matchlen_match2_standalone:
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CMPL DX, $0x02
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JB matchlen_match1_standalone
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MOVW (AX)(SI*1), BX
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CMPW (CX)(SI*1), BX
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JNE matchlen_match1_standalone
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LEAL -2(DX), DX
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LEAL 2(SI), SI
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matchlen_match1_standalone:
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CMPL DX, $0x01
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JB gen_match_len_end
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MOVB (AX)(SI*1), BL
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CMPB (CX)(SI*1), BL
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JNE gen_match_len_end
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INCL SI
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gen_match_len_end:
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MOVQ SI, ret+48(FP)
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RET
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