github.com/twelsh-aw/go/src@v0.0.0-20230516233729-a56fe86a7c81/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  //go:build !plan9
     6  
     7  #include "go_asm.h"
     8  #include "textflag.h"
     9  
    10  // See memclrNoHeapPointers Go doc for important implementation constraints.
    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  #ifdef GO386_softfloat
    33  	JMP	nosse2
    34  #endif
    35  	PXOR	X0, X0
    36  	CMPL	BX, $32
    37  	JBE	_17through32
    38  	CMPL	BX, $64
    39  	JBE	_33through64
    40  	CMPL	BX, $128
    41  	JBE	_65through128
    42  	CMPL	BX, $256
    43  	JBE	_129through256
    44  
    45  loop:
    46  	MOVOU	X0, 0(DI)
    47  	MOVOU	X0, 16(DI)
    48  	MOVOU	X0, 32(DI)
    49  	MOVOU	X0, 48(DI)
    50  	MOVOU	X0, 64(DI)
    51  	MOVOU	X0, 80(DI)
    52  	MOVOU	X0, 96(DI)
    53  	MOVOU	X0, 112(DI)
    54  	MOVOU	X0, 128(DI)
    55  	MOVOU	X0, 144(DI)
    56  	MOVOU	X0, 160(DI)
    57  	MOVOU	X0, 176(DI)
    58  	MOVOU	X0, 192(DI)
    59  	MOVOU	X0, 208(DI)
    60  	MOVOU	X0, 224(DI)
    61  	MOVOU	X0, 240(DI)
    62  	SUBL	$256, BX
    63  	ADDL	$256, DI
    64  	CMPL	BX, $256
    65  	JAE	loop
    66  	JMP	tail
    67  
    68  _1or2:
    69  	MOVB	AX, (DI)
    70  	MOVB	AX, -1(DI)(BX*1)
    71  	RET
    72  _0:
    73  	RET
    74  _3:
    75  	MOVW	AX, (DI)
    76  	MOVB	AX, 2(DI)
    77  	RET
    78  _4:
    79  	// We need a separate case for 4 to make sure we clear pointers atomically.
    80  	MOVL	AX, (DI)
    81  	RET
    82  _5through8:
    83  	MOVL	AX, (DI)
    84  	MOVL	AX, -4(DI)(BX*1)
    85  	RET
    86  _9through16:
    87  	MOVL	AX, (DI)
    88  	MOVL	AX, 4(DI)
    89  	MOVL	AX, -8(DI)(BX*1)
    90  	MOVL	AX, -4(DI)(BX*1)
    91  	RET
    92  _17through32:
    93  	MOVOU	X0, (DI)
    94  	MOVOU	X0, -16(DI)(BX*1)
    95  	RET
    96  _33through64:
    97  	MOVOU	X0, (DI)
    98  	MOVOU	X0, 16(DI)
    99  	MOVOU	X0, -32(DI)(BX*1)
   100  	MOVOU	X0, -16(DI)(BX*1)
   101  	RET
   102  _65through128:
   103  	MOVOU	X0, (DI)
   104  	MOVOU	X0, 16(DI)
   105  	MOVOU	X0, 32(DI)
   106  	MOVOU	X0, 48(DI)
   107  	MOVOU	X0, -64(DI)(BX*1)
   108  	MOVOU	X0, -48(DI)(BX*1)
   109  	MOVOU	X0, -32(DI)(BX*1)
   110  	MOVOU	X0, -16(DI)(BX*1)
   111  	RET
   112  _129through256:
   113  	MOVOU	X0, (DI)
   114  	MOVOU	X0, 16(DI)
   115  	MOVOU	X0, 32(DI)
   116  	MOVOU	X0, 48(DI)
   117  	MOVOU	X0, 64(DI)
   118  	MOVOU	X0, 80(DI)
   119  	MOVOU	X0, 96(DI)
   120  	MOVOU	X0, 112(DI)
   121  	MOVOU	X0, -128(DI)(BX*1)
   122  	MOVOU	X0, -112(DI)(BX*1)
   123  	MOVOU	X0, -96(DI)(BX*1)
   124  	MOVOU	X0, -80(DI)(BX*1)
   125  	MOVOU	X0, -64(DI)(BX*1)
   126  	MOVOU	X0, -48(DI)(BX*1)
   127  	MOVOU	X0, -32(DI)(BX*1)
   128  	MOVOU	X0, -16(DI)(BX*1)
   129  	RET
   130  nosse2:
   131  	MOVL	BX, CX
   132  	SHRL	$2, CX
   133  	REP
   134  	STOSL
   135  	ANDL	$3, BX
   136  	JNE	tail
   137  	RET