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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
19 lines
529 B
LLVM
19 lines
529 B
LLVM
; RUN: llc < %s -mtriple=thumbv7-apple-darwin -mcpu=cortex-a8 -arm-atomic-cfg-tidy=0 -O3 | FileCheck %s
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; rdar://7493908
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; Make sure the result of the first dynamic_alloc isn't copied back to sp more
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; than once. We'll deal with poor codegen later.
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define void @t() nounwind ssp {
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entry:
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; CHECK-LABEL: t:
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%size = mul i32 8, 2
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; CHECK: sub.w r0, sp, #16
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; CHECK: mov sp, r0
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%vla_a = alloca i8, i32 %size, align 8
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; CHECK: sub.w r0, sp, #16
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; CHECK: mov sp, r0
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%vla_b = alloca i8, i32 %size, align 8
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unreachable
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}
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