github.com/q45/go@v0.0.0-20151101211701-a4fb8c13db3f/src/runtime/memmove_plan9_386.s (about)

     1  // Inferno's libkern/memmove-386.s
     2  // http://code.google.com/p/inferno-os/source/browse/libkern/memmove-386.s
     3  //
     4  //         Copyright © 1994-1999 Lucent Technologies Inc.  All rights reserved.
     5  //         Revisions Copyright © 2000-2007 Vita Nuova Holdings Limited (www.vitanuova.com).  All rights reserved.
     6  //         Portions Copyright 2009 The Go Authors. All rights reserved.
     7  //
     8  // Permission is hereby granted, free of charge, to any person obtaining a copy
     9  // of this software and associated documentation files (the "Software"), to deal
    10  // in the Software without restriction, including without limitation the rights
    11  // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
    12  // copies of the Software, and to permit persons to whom the Software is
    13  // furnished to do so, subject to the following conditions:
    14  //
    15  // The above copyright notice and this permission notice shall be included in
    16  // all copies or substantial portions of the Software.
    17  //
    18  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    19  // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    20  // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
    21  // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
    22  // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
    23  // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
    24  // THE SOFTWARE.
    25  
    26  #include "textflag.h"
    27  
    28  TEXT runtime·memmove(SB), NOSPLIT, $0-12
    29  	MOVL	to+0(FP), DI
    30  	MOVL	from+4(FP), SI
    31  	MOVL	n+8(FP), BX
    32  
    33  	// REP instructions have a high startup cost, so we handle small sizes
    34  	// with some straightline code.  The REP MOVSL instruction is really fast
    35  	// for large sizes.  The cutover is approximately 1K.
    36  tail:
    37  	TESTL	BX, BX
    38  	JEQ	move_0
    39  	CMPL	BX, $2
    40  	JBE	move_1or2
    41  	CMPL	BX, $4
    42  	JBE	move_3or4
    43  	CMPL	BX, $8
    44  	JBE	move_5through8
    45  	CMPL	BX, $16
    46  	JBE	move_9through16
    47  
    48  /*
    49   * check and set for backwards
    50   */
    51  	CMPL	SI, DI
    52  	JLS	back
    53  
    54  /*
    55   * forward copy loop
    56   */
    57  forward:	
    58  	MOVL	BX, CX
    59  	SHRL	$2, CX
    60  	ANDL	$3, BX
    61  
    62  	REP;	MOVSL
    63  	JMP	tail
    64  /*
    65   * check overlap
    66   */
    67  back:
    68  	MOVL	SI, CX
    69  	ADDL	BX, CX
    70  	CMPL	CX, DI
    71  	JLS	forward
    72  /*
    73   * whole thing backwards has
    74   * adjusted addresses
    75   */
    76  
    77  	ADDL	BX, DI
    78  	ADDL	BX, SI
    79  	STD
    80  
    81  /*
    82   * copy
    83   */
    84  	MOVL	BX, CX
    85  	SHRL	$2, CX
    86  	ANDL	$3, BX
    87  
    88  	SUBL	$4, DI
    89  	SUBL	$4, SI
    90  	REP;	MOVSL
    91  
    92  	CLD
    93  	ADDL	$4, DI
    94  	ADDL	$4, SI
    95  	SUBL	BX, DI
    96  	SUBL	BX, SI
    97  	JMP	tail
    98  
    99  move_1or2:
   100  	MOVB	(SI), AX
   101  	MOVB	-1(SI)(BX*1), CX
   102  	MOVB	AX, (DI)
   103  	MOVB	CX, -1(DI)(BX*1)
   104  	RET
   105  move_0:
   106  	RET
   107  move_3or4:
   108  	MOVW	(SI), AX
   109  	MOVW	-2(SI)(BX*1), CX
   110  	MOVW	AX, (DI)
   111  	MOVW	CX, -2(DI)(BX*1)
   112  	RET
   113  move_5through8:
   114  	MOVL	(SI), AX
   115  	MOVL	-4(SI)(BX*1), CX
   116  	MOVL	AX, (DI)
   117  	MOVL	CX, -4(DI)(BX*1)
   118  	RET
   119  move_9through16:
   120  	MOVL	(SI), AX
   121  	MOVL	4(SI), CX
   122  	MOVL	-8(SI)(BX*1), DX
   123  	MOVL	-4(SI)(BX*1), BP
   124  	MOVL	AX, (DI)
   125  	MOVL	CX, 4(DI)
   126  	MOVL	DX, -8(DI)(BX*1)
   127  	MOVL	BP, -4(DI)(BX*1)
   128  	RET