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68058edc39
memclrNoHeapPointers is the underlying implementation of typedmemclr and memclrHasPointers, so it still needs to write pointer-aligned words atomically. Document this requirement. Updates #41428. Change-Id: Ice00dee5de7a96a50e51ff019fcef069e8a8406a Reviewed-on: https://go-review.googlesource.com/c/go/+/287692 Trust: Cherry Zhang <cherryyz@google.com> Reviewed-by: Keith Randall <khr@golang.org>
59 lines
983 B
ArmAsm
59 lines
983 B
ArmAsm
// Copyright 2014 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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// See memclrNoHeapPointers Go doc for important implementation constraints.
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// func memclrNoHeapPointers(ptr unsafe.Pointer, n uintptr)
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TEXT runtime·memclrNoHeapPointers(SB), NOSPLIT, $0-8
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MOVL ptr+0(FP), DI
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MOVL n+4(FP), BX
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XORL AX, AX
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tail:
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TESTL BX, BX
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JEQ _0
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CMPL BX, $2
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JBE _1or2
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CMPL BX, $4
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JB _3
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JE _4
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CMPL BX, $8
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JBE _5through8
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CMPL BX, $16
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JBE _9through16
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MOVL BX, CX
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SHRL $2, CX
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REP
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STOSL
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ANDL $3, BX
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JNE tail
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RET
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_1or2:
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MOVB AX, (DI)
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MOVB AX, -1(DI)(BX*1)
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RET
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_0:
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RET
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_3:
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MOVW AX, (DI)
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MOVB AX, 2(DI)
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RET
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_4:
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// We need a separate case for 4 to make sure we clear pointers atomically.
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MOVL AX, (DI)
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RET
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_5through8:
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MOVL AX, (DI)
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MOVL AX, -4(DI)(BX*1)
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RET
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_9through16:
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MOVL AX, (DI)
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MOVL AX, 4(DI)
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MOVL AX, -8(DI)(BX*1)
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MOVL AX, -4(DI)(BX*1)
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RET
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