2015-09-30 15:47:19 -06:00
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// Copyright 2015 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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2015-11-10 16:45:51 -07:00
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// +build amd64,!appengine,!gccgo
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2015-09-30 15:47:19 -06:00
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#include "textflag.h"
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// func havePOPCNT() bool
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TEXT ·havePOPCNT(SB),4,$0
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MOVQ $1, AX
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CPUID
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SHRQ $23, CX
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ANDQ $1, CX
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MOVB CX, ret+0(FP)
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RET
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// func popcnt(word) int
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TEXT ·popcnt(SB),NOSPLIT,$0-8
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XORQ AX, AX
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MOVQ x+0(FP), SI
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// POPCNT (SI), AX is not recognized by Go assembler,
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// so we assemble it ourselves.
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BYTE $0xf3
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BYTE $0x48
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BYTE $0x0f
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BYTE $0xb8
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BYTE $0xc6
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MOVQ AX, ret+8(FP)
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RET
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