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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
34 lines
1.3 KiB
LLVM
34 lines
1.3 KiB
LLVM
; RUN: llc < %s -mtriple=thumbv7-apple-darwin -arm-atomic-cfg-tidy=0 | FileCheck %s
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; RUN: llc < %s -mtriple=thumbv7-apple-darwin -arm-atomic-cfg-tidy=0 -arm-default-it | FileCheck %s
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; RUN: llc < %s -mtriple=thumbv8-apple-darwin -arm-atomic-cfg-tidy=0 -arm-no-restrict-it | FileCheck %s
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; There shouldn't be a unconditional branch at end of bb52.
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; rdar://7184787
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@posed = external global i64 ; <i64*> [#uses=1]
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define i1 @ab_bb52(i64 %.reload78, i64* %.out, i64* %.out1) nounwind {
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newFuncRoot:
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br label %bb52
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bb52.bb55_crit_edge.exitStub: ; preds = %bb52
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store i64 %0, i64* %.out
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store i64 %2, i64* %.out1
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ret i1 true
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bb52.bb53_crit_edge.exitStub: ; preds = %bb52
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store i64 %0, i64* %.out
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store i64 %2, i64* %.out1
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ret i1 false
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bb52: ; preds = %newFuncRoot
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; CHECK: movne
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; CHECK: moveq
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; CHECK: pop
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%0 = load i64* @posed, align 4 ; <i64> [#uses=3]
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%1 = sub i64 %0, %.reload78 ; <i64> [#uses=1]
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%2 = ashr i64 %1, 1 ; <i64> [#uses=3]
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%3 = icmp eq i64 %2, 0 ; <i1> [#uses=1]
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br i1 %3, label %bb52.bb55_crit_edge.exitStub, label %bb52.bb53_crit_edge.exitStub
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}
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