github.com/geraldss/go/src@v0.0.0-20210511222824-ac7d0ebfc235/runtime/memclr_386.s (about)

     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 "go_asm.h"
     8  #include "textflag.h"
     9  
    10  // NOTE: Windows externalthreadhandler expects memclr to preserve DX.
    11  
    12  // func memclrNoHeapPointers(ptr unsafe.Pointer, n uintptr)
    13  TEXT runtime·memclrNoHeapPointers(SB), NOSPLIT, $0-8
    14  	MOVL	ptr+0(FP), DI
    15  	MOVL	n+4(FP), BX
    16  	XORL	AX, AX
    17  
    18  	// MOVOU seems always faster than REP STOSL.
    19  tail:
    20  	// BSR+branch table make almost all memmove/memclr benchmarks worse. Not worth doing.
    21  	TESTL	BX, BX
    22  	JEQ	_0
    23  	CMPL	BX, $2
    24  	JBE	_1or2
    25  	CMPL	BX, $4
    26  	JB	_3
    27  	JE	_4
    28  	CMPL	BX, $8
    29  	JBE	_5through8
    30  	CMPL	BX, $16
    31  	JBE	_9through16
    32  	CMPB	internal∕cpu·X86+const_offsetX86HasSSE2(SB), $1
    33  	JNE	nosse2
    34  	PXOR	X0, X0
    35  	CMPL	BX, $32
    36  	JBE	_17through32
    37  	CMPL	BX, $64
    38  	JBE	_33through64
    39  	CMPL	BX, $128
    40  	JBE	_65through128
    41  	CMPL	BX, $256
    42  	JBE	_129through256
    43  
    44  loop:
    45  	MOVOU	X0, 0(DI)
    46  	MOVOU	X0, 16(DI)
    47  	MOVOU	X0, 32(DI)
    48  	MOVOU	X0, 48(DI)
    49  	MOVOU	X0, 64(DI)
    50  	MOVOU	X0, 80(DI)
    51  	MOVOU	X0, 96(DI)
    52  	MOVOU	X0, 112(DI)
    53  	MOVOU	X0, 128(DI)
    54  	MOVOU	X0, 144(DI)
    55  	MOVOU	X0, 160(DI)
    56  	MOVOU	X0, 176(DI)
    57  	MOVOU	X0, 192(DI)
    58  	MOVOU	X0, 208(DI)
    59  	MOVOU	X0, 224(DI)
    60  	MOVOU	X0, 240(DI)
    61  	SUBL	$256, BX
    62  	ADDL	$256, DI
    63  	CMPL	BX, $256
    64  	JAE	loop
    65  	JMP	tail
    66  
    67  _1or2:
    68  	MOVB	AX, (DI)
    69  	MOVB	AX, -1(DI)(BX*1)
    70  	RET
    71  _0:
    72  	RET
    73  _3:
    74  	MOVW	AX, (DI)
    75  	MOVB	AX, 2(DI)
    76  	RET
    77  _4:
    78  	// We need a separate case for 4 to make sure we clear pointers atomically.
    79  	MOVL	AX, (DI)
    80  	RET
    81  _5through8:
    82  	MOVL	AX, (DI)
    83  	MOVL	AX, -4(DI)(BX*1)
    84  	RET
    85  _9through16:
    86  	MOVL	AX, (DI)
    87  	MOVL	AX, 4(DI)
    88  	MOVL	AX, -8(DI)(BX*1)
    89  	MOVL	AX, -4(DI)(BX*1)
    90  	RET
    91  _17through32:
    92  	MOVOU	X0, (DI)
    93  	MOVOU	X0, -16(DI)(BX*1)
    94  	RET
    95  _33through64:
    96  	MOVOU	X0, (DI)
    97  	MOVOU	X0, 16(DI)
    98  	MOVOU	X0, -32(DI)(BX*1)
    99  	MOVOU	X0, -16(DI)(BX*1)
   100  	RET
   101  _65through128:
   102  	MOVOU	X0, (DI)
   103  	MOVOU	X0, 16(DI)
   104  	MOVOU	X0, 32(DI)
   105  	MOVOU	X0, 48(DI)
   106  	MOVOU	X0, -64(DI)(BX*1)
   107  	MOVOU	X0, -48(DI)(BX*1)
   108  	MOVOU	X0, -32(DI)(BX*1)
   109  	MOVOU	X0, -16(DI)(BX*1)
   110  	RET
   111  _129through256:
   112  	MOVOU	X0, (DI)
   113  	MOVOU	X0, 16(DI)
   114  	MOVOU	X0, 32(DI)
   115  	MOVOU	X0, 48(DI)
   116  	MOVOU	X0, 64(DI)
   117  	MOVOU	X0, 80(DI)
   118  	MOVOU	X0, 96(DI)
   119  	MOVOU	X0, 112(DI)
   120  	MOVOU	X0, -128(DI)(BX*1)
   121  	MOVOU	X0, -112(DI)(BX*1)
   122  	MOVOU	X0, -96(DI)(BX*1)
   123  	MOVOU	X0, -80(DI)(BX*1)
   124  	MOVOU	X0, -64(DI)(BX*1)
   125  	MOVOU	X0, -48(DI)(BX*1)
   126  	MOVOU	X0, -32(DI)(BX*1)
   127  	MOVOU	X0, -16(DI)(BX*1)
   128  	RET
   129  nosse2:
   130  	MOVL	BX, CX
   131  	SHRL	$2, CX
   132  	REP
   133  	STOSL
   134  	ANDL	$3, BX
   135  	JNE	tail
   136  	RET