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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
35 lines
666 B
LLVM
35 lines
666 B
LLVM
; rdar://8465407
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; RUN: llc < %s -mtriple=thumbv7-apple-ios -arm-atomic-cfg-tidy=0 | FileCheck %s
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%struct.buf = type opaque
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declare void @bar() nounwind optsize
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define void @foo() nounwind optsize {
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; CHECK-LABEL: foo:
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; CHECK: push
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; CHECK: mov r7, sp
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; CHECK: sub sp, #4
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entry:
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%m.i = alloca %struct.buf*, align 4
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br label %bb
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bb:
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br i1 undef, label %bb3, label %bb2
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bb2:
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call void @bar() nounwind optsize
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br i1 undef, label %bb, label %bb3
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bb3:
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br i1 undef, label %return, label %bb
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return:
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; CHECK: %return
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; 'mov sp, r7' would have left sp in an invalid state
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; CHECK-NOT: mov sp, r7
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; CHECK-NOT: sub, sp, #4
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; CHECK: add sp, #4
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ret void
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}
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