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https://github.com/golang/go
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4b7d5f0b94
Make sure that we're moving or zeroing pointers atomically. Anything that is a multiple of pointer size and at least pointer aligned might have pointers in it. All the code looks ok except for the 1-pointer-sized moves. Fixes #13160 Update #12552 Change-Id: Ib97d9b918fa9f4cc5c56c67ed90255b7fdfb7b45 Reviewed-on: https://go-review.googlesource.com/16668 Reviewed-by: Dmitry Vyukov <dvyukov@google.com> Run-TryBot: Keith Randall <khr@golang.org> TryBot-Result: Gobot Gobot <gobot@golang.org>
53 lines
934 B
ArmAsm
53 lines
934 B
ArmAsm
// Copyright 2013 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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#include "textflag.h"
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// This could use MOVSQ, but we use MOVSL so that if an object ends in
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// a 4 byte pointer, we copy it as a unit instead of byte by byte.
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TEXT runtime·memmove(SB), NOSPLIT, $0-12
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MOVL to+0(FP), DI
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MOVL from+4(FP), SI
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MOVL n+8(FP), BX
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CMPL SI, DI
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JLS back
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forward:
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MOVL BX, CX
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SHRL $2, CX
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ANDL $3, BX
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REP; MOVSL
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MOVL BX, CX
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REP; MOVSB
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RET
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back:
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MOVL SI, CX
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ADDL BX, CX
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CMPL CX, DI
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JLS forward
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ADDL BX, DI
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ADDL BX, SI
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STD
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MOVL BX, CX
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SHRL $2, CX
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ANDL $3, BX
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SUBL $4, DI
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SUBL $4, SI
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REP; MOVSL
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ADDL $3, DI
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ADDL $3, SI
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MOVL BX, CX
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REP; MOVSB
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CLD
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// Note: we copy only 4 bytes at a time so that the tail is at most
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// 3 bytes. That guarantees that we aren't copying pointers with MOVSB.
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// See issue 13160.
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RET
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