github.com/twelsh-aw/go/src@v0.0.0-20230516233729-a56fe86a7c81/runtime/memmove_plan9_386.s (about)

     1  // Inferno's libkern/memmove-386.s
     2  // https://bitbucket.org/inferno-os/inferno-os/src/master/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.
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     9  // of this software and associated documentation files (the "Software"), to deal
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    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  // See memmove Go doc for important implementation constraints.
    29  
    30  // func memmove(to, from unsafe.Pointer, n uintptr)
    31  TEXT runtime·memmove(SB), NOSPLIT, $0-12
    32  	MOVL	to+0(FP), DI
    33  	MOVL	from+4(FP), SI
    34  	MOVL	n+8(FP), BX
    35  
    36  	// REP instructions have a high startup cost, so we handle small sizes
    37  	// with some straightline code. The REP MOVSL instruction is really fast
    38  	// for large sizes. The cutover is approximately 1K.
    39  tail:
    40  	TESTL	BX, BX
    41  	JEQ	move_0
    42  	CMPL	BX, $2
    43  	JBE	move_1or2
    44  	CMPL	BX, $4
    45  	JB	move_3
    46  	JE	move_4
    47  	CMPL	BX, $8
    48  	JBE	move_5through8
    49  	CMPL	BX, $16
    50  	JBE	move_9through16
    51  
    52  /*
    53   * check and set for backwards
    54   */
    55  	CMPL	SI, DI
    56  	JLS	back
    57  
    58  /*
    59   * forward copy loop
    60   */
    61  forward:
    62  	MOVL	BX, CX
    63  	SHRL	$2, CX
    64  	ANDL	$3, BX
    65  
    66  	REP;	MOVSL
    67  	JMP	tail
    68  /*
    69   * check overlap
    70   */
    71  back:
    72  	MOVL	SI, CX
    73  	ADDL	BX, CX
    74  	CMPL	CX, DI
    75  	JLS	forward
    76  /*
    77   * whole thing backwards has
    78   * adjusted addresses
    79   */
    80  
    81  	ADDL	BX, DI
    82  	ADDL	BX, SI
    83  	STD
    84  
    85  /*
    86   * copy
    87   */
    88  	MOVL	BX, CX
    89  	SHRL	$2, CX
    90  	ANDL	$3, BX
    91  
    92  	SUBL	$4, DI
    93  	SUBL	$4, SI
    94  	REP;	MOVSL
    95  
    96  	CLD
    97  	ADDL	$4, DI
    98  	ADDL	$4, SI
    99  	SUBL	BX, DI
   100  	SUBL	BX, SI
   101  	JMP	tail
   102  
   103  move_1or2:
   104  	MOVB	(SI), AX
   105  	MOVB	-1(SI)(BX*1), CX
   106  	MOVB	AX, (DI)
   107  	MOVB	CX, -1(DI)(BX*1)
   108  	RET
   109  move_0:
   110  	RET
   111  move_3:
   112  	MOVW	(SI), AX
   113  	MOVB	2(SI), CX
   114  	MOVW	AX, (DI)
   115  	MOVB	CX, 2(DI)
   116  	RET
   117  move_4:
   118  	// We need a separate case for 4 to make sure we write pointers atomically.
   119  	MOVL	(SI), AX
   120  	MOVL	AX, (DI)
   121  	RET
   122  move_5through8:
   123  	MOVL	(SI), AX
   124  	MOVL	-4(SI)(BX*1), CX
   125  	MOVL	AX, (DI)
   126  	MOVL	CX, -4(DI)(BX*1)
   127  	RET
   128  move_9through16:
   129  	MOVL	(SI), AX
   130  	MOVL	4(SI), CX
   131  	MOVL	-8(SI)(BX*1), DX
   132  	MOVL	-4(SI)(BX*1), BP
   133  	MOVL	AX, (DI)
   134  	MOVL	CX, 4(DI)
   135  	MOVL	DX, -8(DI)(BX*1)
   136  	MOVL	BP, -4(DI)(BX*1)
   137  	RET