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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
12 lines
293 B
LLVM
12 lines
293 B
LLVM
; RUN: llc -march=arm64 -mtriple=arm64-apple-ios -aarch64-atomic-cfg-tidy=0 < %s | FileCheck %s
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; rdar://11935841
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define void @t1() nounwind ssp {
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entry:
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; CHECK-LABEL: t1:
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; CHECK-NOT: add x{{[0-9]+}}, sp
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; CHECK: stp x28, x27, [sp, #-16]!
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%v = alloca [288 x i32], align 4
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unreachable
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}
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