github.com/megatontech/mynoteforgo@v0.0.0-20200507084910-5d0c6ea6e890/源码/runtime/memmove_ppc64x.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 ppc64 ppc64le
     6  
     7  #include "textflag.h"
     8  
     9  // func memmove(to, from unsafe.Pointer, n uintptr)
    10  TEXT runtime·memmove(SB), NOSPLIT|NOFRAME, $0-24
    11  	MOVD	to+0(FP), R3
    12  	MOVD	from+8(FP), R4
    13  	MOVD	n+16(FP), R5
    14  
    15  	// Determine if there are doublewords to
    16  	// copy so a more efficient move can be done
    17  check:
    18  	ANDCC	$7, R5, R7	// R7: bytes to copy
    19  	SRD	$3, R5, R6	// R6: double words to copy
    20  	CMP	R6, $0, CR1	// CR1[EQ] set if no double words to copy
    21  
    22  	// Determine overlap by subtracting dest - src and comparing against the
    23  	// length.  The catches the cases where src and dest are in different types
    24  	// of storage such as stack and static to avoid doing backward move when not
    25  	// necessary.
    26  
    27  	SUB	R4, R3, R8	// dest - src
    28  	CMPU	R8, R5, CR2	// < len?
    29  	BC	12, 8, backward // BLT CR2 backward
    30  
    31  	// Copying forward if no overlap.
    32  
    33  	BC	12, 6, noforwardlarge	// "BEQ CR1, noforwardlarge"
    34  	SRDCC	$2,R6,R8		// 32 byte chunks?
    35  	BNE	forward32setup		//
    36  	MOVD	R6,CTR			// R6 = number of double words
    37  
    38  	// Move double words
    39  
    40  forward8:
    41  	MOVD    0(R4), R8		// double word
    42  	ADD     $8,R4
    43  	MOVD    R8, 0(R3)		//
    44  	ADD     $8,R3
    45  	BC      16, 0, forward8
    46  	BR	noforwardlarge		// handle remainder
    47  
    48  	// Prepare for moves of 32 bytes at a time.
    49  
    50  forward32setup:
    51  	DCBTST	(R3)			// prepare data cache
    52  	DCBT	(R4)
    53  	MOVD	R8, CTR			// double work count
    54  	MOVD	$16, R8
    55  
    56  forward32:
    57  	LXVD2X	(R4+R0), VS32		// load 16 bytes
    58  	LXVD2X	(R4+R8), VS33
    59  	ADD	$32, R4
    60  	STXVD2X	VS32, (R3+R0)		// store 16 bytes
    61  	STXVD2X	VS33, (R3+R8)
    62  	ADD	$32,R3			// bump up for next set
    63  	BC	16, 0, forward32	// continue
    64  	RLDCLCC	$61,R5,$3,R6		// remaining doublewords
    65  	BEQ	noforwardlarge
    66  	MOVD	R6,CTR			// set up the CTR
    67  	BR	forward8
    68  
    69  noforwardlarge:
    70  	CMP	R7,$0			// any remaining bytes
    71  	BC	4, 1, LR		// ble lr
    72  
    73  forwardtail:
    74  	MOVD	R7, CTR			// move tail bytes
    75  
    76  forwardtailloop:
    77  	MOVBZ	0(R4), R8		// move single bytes
    78  	ADD	$1,R4
    79  	MOVBZ	R8, 0(R3)
    80  	ADD	$1,R3
    81  	BC	16, 0, forwardtailloop
    82  	RET
    83  
    84  backward:
    85  	// Copying backwards proceeds by copying R7 bytes then copying R6 double words.
    86  	// R3 and R4 are advanced to the end of the destination/source buffers
    87  	// respectively and moved back as we copy.
    88  
    89  	ADD	R5, R4, R4		// end of source
    90  	ADD	R3, R5, R3		// end of dest
    91  
    92  	BEQ	nobackwardtail		// earlier condition
    93  
    94  	MOVD	R7, CTR			// bytes to move
    95  
    96  backwardtailloop:
    97  	MOVBZ 	-1(R4), R8		// point to last byte
    98  	SUB	$1,R4
    99  	MOVBZ 	R8, -1(R3)
   100  	SUB	$1,R3
   101  	BC	16, 0, backwardtailloop // bndz
   102  
   103  nobackwardtail:
   104  	BC	4, 5, LR		// ble CR1 lr
   105  
   106  backwardlarge:
   107  	MOVD	R6, CTR
   108  	SUB	R3, R4, R9		// Use vsx if moving
   109  	CMP	R9, $32			// at least 32 byte chunks
   110  	BLT	backwardlargeloop	// and distance >= 32
   111  	SRDCC	$2,R6,R8		// 32 byte chunks
   112  	BNE	backward32setup
   113  
   114  backwardlargeloop:
   115  	MOVD 	-8(R4), R8
   116  	SUB	$8,R4
   117  	MOVD 	R8, -8(R3)
   118  	SUB	$8,R3
   119  	BC	16, 0, backwardlargeloop // bndz
   120  	RET
   121  
   122  backward32setup:
   123  	MOVD	R8, CTR			// set up loop ctr
   124  	MOVD	$16, R8			// 32 bytes at at time
   125  
   126  backward32loop:
   127  	SUB	$32, R4
   128  	SUB	$32, R3
   129  	LXVD2X	(R4+R0), VS32           // load 16 bytes
   130  	LXVD2X	(R4+R8), VS33
   131  	STXVD2X	VS32, (R3+R0)           // store 16 bytes
   132  	STXVD2X	VS33, (R3+R8)
   133  	BC      16, 0, backward32loop   // bndz
   134  	BC	4, 5, LR		// ble CR1 lr
   135  	MOVD	R6, CTR
   136  	BR	backwardlargeloop