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	The C and C++ semantics for compare_exchange require it to return a bool
indicating success. This gets mapped to LLVM IR which follows each cmpxchg with
an icmp of the value loaded against the desired value.
When lowered to ldxr/stxr loops, this extra comparison is redundant: its
results are implicit in the control-flow of the function.
This commit makes two changes: it replaces that icmp with appropriate PHI
nodes, and then makes sure earlyCSE is called after expansion to actually make
use of the opportunities revealed.
I've also added -{arm,aarch64}-enable-atomic-tidy options, so that
existing fragile tests aren't perturbed too much by the change. Many
of them either rely on undef/unreachable too pervasively to be
restored to something well-defined (particularly while making sure
they test the same obscure assert from many years ago), or depend on a
particular CFG shape, which is disrupted by SimplifyCFG.
rdar://problem/16227836
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209883 91177308-0d34-0410-b5e6-96231b3b80d8
		
	
		
			
				
	
	
		
			50 lines
		
	
	
		
			967 B
		
	
	
	
		
			LLVM
		
	
	
	
	
	
			
		
		
	
	
			50 lines
		
	
	
		
			967 B
		
	
	
	
		
			LLVM
		
	
	
	
	
	
; RUN: llc -mtriple=arm-eabi -arm-atomic-cfg-tidy=0 -mattr=+v6,+vfp2 %s -o - | FileCheck %s
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@i = weak global i32 0		; <i32*> [#uses=2]
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@u = weak global i32 0		; <i32*> [#uses=2]
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define i32 @foo1(float *%x) {
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        %tmp1 = load float* %x
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	%tmp2 = bitcast float %tmp1 to i32
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	ret i32 %tmp2
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}
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define i64 @foo2(double *%x) {
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        %tmp1 = load double* %x
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	%tmp2 = bitcast double %tmp1 to i64
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	ret i64 %tmp2
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}
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define void @foo5(float %x) {
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	%tmp1 = fptosi float %x to i32
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	store i32 %tmp1, i32* @i
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	ret void
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}
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define void @foo6(float %x) {
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	%tmp1 = fptoui float %x to i32
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	store i32 %tmp1, i32* @u
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	ret void
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}
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define void @foo7(double %x) {
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	%tmp1 = fptosi double %x to i32
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	store i32 %tmp1, i32* @i
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	ret void
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}
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define void @foo8(double %x) {
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	%tmp1 = fptoui double %x to i32
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	store i32 %tmp1, i32* @u
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	ret void
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}
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define void @foo9(double %x) {
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	%tmp = fptoui double %x to i16
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	store i16 %tmp, i16* null
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	ret void
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}
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; CHECK-LABEL: foo9:
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; CHECK: 	vmov	r0, s0
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