memclr_386.s

Documentation: runtime

     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)
    13TEXT 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.
    19tail:
    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
    45loop:
    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
   130nosse2:
   131	MOVL	BX, CX
   132	SHRL	$2, CX
   133	REP
   134	STOSL
   135	ANDL	$3, BX
   136	JNE	tail
   137	RET
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