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86b0ea6447
asm_arm.s was using ldrex which does not work on armv5. Tested on Sheevaplug. R=rsc, kaib CC=golang-dev https://golang.org/cl/214049
41 lines
751 B
ArmAsm
41 lines
751 B
ArmAsm
// Copyright 2009 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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// This version works on pre v6 architectures
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// func cas(val *int32, old, new int32) bool
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// Atomically:
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// if *val == old {
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// *val = new;
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// return true;
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// }else
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// return false;
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TEXT ·cas(SB),7,$0
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MOVW 0(FP), R0 // *val
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MOVW 4(FP), R1 // old
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MOVW 8(FP), R2 // new
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MOVW $1, R3
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MOVW $cas_mutex(SB), R4
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l:
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SWPW (R4), R3 // acquire mutex
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CMP $0, R3
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BNE fail0
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MOVW (R0), R5
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CMP R1, R5
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BNE fail1
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MOVW R2, (R0)
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MOVW R3, (R4) // release mutex
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MOVW $1, R0
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MOVW R0, 16(SP)
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RET
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fail1:
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MOVW R3, (R4) // release mutex
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fail0:
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MOVW $0, R0
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MOVW R0, 16(SP)
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RET
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