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      1 // Copyright 2014 The Go Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style
      3 // license that can be found in the LICENSE file.
      4 
      5 // +build !plan9
      6 
      7 #include "textflag.h"
      8 
      9 // NOTE: Windows externalthreadhandler expects memclr to preserve DX.
     10 
     11 // void runtimememclr(void*, uintptr)
     12 TEXT runtimememclr(SB), NOSPLIT, $0-16
     13 	MOVQ	ptr+0(FP), DI
     14 	MOVQ	n+8(FP), BX
     15 	XORQ	AX, AX
     16 
     17 	// MOVOU seems always faster than REP STOSQ.
     18 tail:
     19 	TESTQ	BX, BX
     20 	JEQ	_0
     21 	CMPQ	BX, $2
     22 	JBE	_1or2
     23 	CMPQ	BX, $4
     24 	JBE	_3or4
     25 	CMPQ	BX, $8
     26 	JBE	_5through8
     27 	CMPQ	BX, $16
     28 	JBE	_9through16
     29 	PXOR	X0, X0
     30 	CMPQ	BX, $32
     31 	JBE	_17through32
     32 	CMPQ	BX, $64
     33 	JBE	_33through64
     34 	CMPQ	BX, $128
     35 	JBE	_65through128
     36 	CMPQ	BX, $256
     37 	JBE	_129through256
     38 	// TODO: use branch table and BSR to make this just a single dispatch
     39 	// TODO: for really big clears, use MOVNTDQ.
     40 
     41 loop:
     42 	MOVOU	X0, 0(DI)
     43 	MOVOU	X0, 16(DI)
     44 	MOVOU	X0, 32(DI)
     45 	MOVOU	X0, 48(DI)
     46 	MOVOU	X0, 64(DI)
     47 	MOVOU	X0, 80(DI)
     48 	MOVOU	X0, 96(DI)
     49 	MOVOU	X0, 112(DI)
     50 	MOVOU	X0, 128(DI)
     51 	MOVOU	X0, 144(DI)
     52 	MOVOU	X0, 160(DI)
     53 	MOVOU	X0, 176(DI)
     54 	MOVOU	X0, 192(DI)
     55 	MOVOU	X0, 208(DI)
     56 	MOVOU	X0, 224(DI)
     57 	MOVOU	X0, 240(DI)
     58 	SUBQ	$256, BX
     59 	ADDQ	$256, DI
     60 	CMPQ	BX, $256
     61 	JAE	loop
     62 	JMP	tail
     63 
     64 _1or2:
     65 	MOVB	AX, (DI)
     66 	MOVB	AX, -1(DI)(BX*1)
     67 	RET
     68 _0:
     69 	RET
     70 _3or4:
     71 	MOVW	AX, (DI)
     72 	MOVW	AX, -2(DI)(BX*1)
     73 	RET
     74 _5through8:
     75 	MOVL	AX, (DI)
     76 	MOVL	AX, -4(DI)(BX*1)
     77 	RET
     78 _9through16:
     79 	MOVQ	AX, (DI)
     80 	MOVQ	AX, -8(DI)(BX*1)
     81 	RET
     82 _17through32:
     83 	MOVOU	X0, (DI)
     84 	MOVOU	X0, -16(DI)(BX*1)
     85 	RET
     86 _33through64:
     87 	MOVOU	X0, (DI)
     88 	MOVOU	X0, 16(DI)
     89 	MOVOU	X0, -32(DI)(BX*1)
     90 	MOVOU	X0, -16(DI)(BX*1)
     91 	RET
     92 _65through128:
     93 	MOVOU	X0, (DI)
     94 	MOVOU	X0, 16(DI)
     95 	MOVOU	X0, 32(DI)
     96 	MOVOU	X0, 48(DI)
     97 	MOVOU	X0, -64(DI)(BX*1)
     98 	MOVOU	X0, -48(DI)(BX*1)
     99 	MOVOU	X0, -32(DI)(BX*1)
    100 	MOVOU	X0, -16(DI)(BX*1)
    101 	RET
    102 _129through256:
    103 	MOVOU	X0, (DI)
    104 	MOVOU	X0, 16(DI)
    105 	MOVOU	X0, 32(DI)
    106 	MOVOU	X0, 48(DI)
    107 	MOVOU	X0, 64(DI)
    108 	MOVOU	X0, 80(DI)
    109 	MOVOU	X0, 96(DI)
    110 	MOVOU	X0, 112(DI)
    111 	MOVOU	X0, -128(DI)(BX*1)
    112 	MOVOU	X0, -112(DI)(BX*1)
    113 	MOVOU	X0, -96(DI)(BX*1)
    114 	MOVOU	X0, -80(DI)(BX*1)
    115 	MOVOU	X0, -64(DI)(BX*1)
    116 	MOVOU	X0, -48(DI)(BX*1)
    117 	MOVOU	X0, -32(DI)(BX*1)
    118 	MOVOU	X0, -16(DI)(BX*1)
    119 	RET
    120