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3bb84c9bcc
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
llvm-svn: 209883
18 lines
448 B
LLVM
18 lines
448 B
LLVM
; RUN: llc -verify-machineinstrs -o - %s -mtriple=aarch64-linux-gnu -aarch64-atomic-cfg-tidy=0 | FileCheck %s
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@stored_label = global i8* null
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define void @foo() {
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; CHECK-LABEL: foo:
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%lab = load i8** @stored_label
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indirectbr i8* %lab, [label %otherlab, label %retlab]
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; CHECK: adrp {{x[0-9]+}}, stored_label
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; CHECK: ldr {{x[0-9]+}}, [{{x[0-9]+}}, {{#?}}:lo12:stored_label]
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; CHECK: br {{x[0-9]+}}
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otherlab:
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ret void
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retlab:
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ret void
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}
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