go/src/runtime/memmove_ppc64x.s

// Copyright 2014 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// +build ppc64 ppc64le

#include "textflag.h"

// void runtime·memmove(void*, void*, uintptr)
TEXT runtime·memmove(SB), NOSPLIT|NOFRAME, $0-24
	MOVD	to+0(FP), R3
	MOVD	from+8(FP), R4
	MOVD	n+16(FP), R5

	// Determine if there are doublewords to
	// copy so a more efficient move can be done
check:
	ANDCC	$7, R5, R7	// R7: bytes to copy
	SRAD	$3, R5, R6	// R6: double words to copy
	CMP	R6, $0, CR1	// CR1[EQ] set if no double words to copy

	// Determine overlap by subtracting dest - src and comparing against the
	// length.  The catches the cases where src and dest are in different types
	// of storage such as stack and static to avoid doing backward move when not
	// necessary.

	SUB	R4, R3, R8	// dest - src
	CMPU	R8, R5, CR2	// < len?
	BC	12, 8, backward // BLT CR2 backward

	// Copying forward if no overlap.

	BC	12, 6, noforwardlarge	// "BEQ CR1, noforwardlarge"
	MOVD	R6,CTR			// R6 = number of double words
	SRADCC	$2,R6,R8		// 32 byte chunks?
	BNE	forward32setup		//

	// Move double words

forward8:
	MOVD    0(R4), R8		// double word
	ADD     $8,R4
	MOVD    R8, 0(R3)		//
	ADD     $8,R3
	BC      16, 0, forward8
	BR	noforwardlarge		// handle remainder

	// Prepare for moves of 32 bytes at a time.

forward32setup:
	DCBTST	(R3)			// prepare data cache
	DCBT	(R4)
	MOVD	R8, CTR			// double work count

forward32:
	MOVD	0(R4), R8		// load 4 double words
	MOVD	8(R4), R9
	MOVD	16(R4), R14
	MOVD	24(R4), R15
	ADD	$32,R4
	MOVD	R8, 0(R3)		// store those 4
	MOVD	R9, 8(R3)
	MOVD	R14,16(R3)
	MOVD	R15,24(R3)
	ADD	$32,R3			// bump up for next set
	BC	16, 0, forward32	// continue
	RLDCLCC	$61,R5,$3,R6		// remaining doublewords
	BEQ	noforwardlarge
	MOVD	R6,CTR			// set up the CTR
	BR	forward8

noforwardlarge:
	CMP	R7,$0			// any remaining bytes
	BC	4, 1, LR

forwardtail:
	MOVD	R7, CTR			// move tail bytes

forwardtailloop:
	MOVBZ	0(R4), R8		// move single bytes
	ADD	$1,R4
	MOVBZ	R8, 0(R3)
	ADD	$1,R3
	BC	16, 0, forwardtailloop
	RET

backward:
	// Copying backwards proceeds by copying R7 bytes then copying R6 double words.
	// R3 and R4 are advanced to the end of the destination/source buffers
	// respectively and moved back as we copy.

	ADD	R5, R4, R4		// end of source
	ADD	R3, R5, R3		// end of dest

	BEQ	nobackwardtail		// earlier condition

	MOVD	R7, CTR			// bytes to move

backwardtailloop:
	MOVBZ 	-1(R4), R8		// point to last byte
	SUB	$1,R4
	MOVBZ 	R8, -1(R3)
	SUB	$1,R3
	BC	16, 0, backwardtailloop

nobackwardtail:
	CMP	R6,$0
	BC	4, 5, LR

backwardlarge:
	MOVD	R6, CTR

backwardlargeloop:
	MOVD 	-8(R4), R8
	SUB	$8,R4
	MOVD 	R8, -8(R3)
	SUB	$8,R3
	BC	16, 0, backwardlargeloop	//
	RET