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d0dbe02fd2
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
36 lines
1.0 KiB
LLVM
36 lines
1.0 KiB
LLVM
; RUN: llc < %s -mtriple=thumbv7-apple-darwin -mcpu=cortex-a8 -arm-atomic-cfg-tidy=0 | FileCheck %s
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; rdar://7354379
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declare double @foo(double) nounwind readnone
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define void @t(i32 %c, double %b) {
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entry:
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%cmp1 = icmp ne i32 %c, 0
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br i1 %cmp1, label %bb3, label %bb1
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bb1: ; preds = %entry
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unreachable
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bb3: ; preds = %entry
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%cmp2 = icmp ne i32 %c, 0
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br i1 %cmp2, label %bb7, label %bb5
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bb5: ; preds = %bb3
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unreachable
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bb7: ; preds = %bb3
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%cmp3 = icmp ne i32 %c, 0
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br i1 %cmp3, label %bb11, label %bb9
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bb9: ; preds = %bb7
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; CHECK: cmp r0, #0
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; CHECK-NEXT: cbnz
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%0 = tail call double @foo(double %b) nounwind readnone ; <double> [#uses=0]
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br label %bb11
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bb11: ; preds = %bb9, %bb7
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%1 = getelementptr i32* undef, i32 0
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store i32 0, i32* %1
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ret void
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}
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