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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
33 lines
893 B
LLVM
33 lines
893 B
LLVM
; RUN: llc < %s -mtriple=thumbv7-apple-ios -arm-atomic-cfg-tidy=0 | FileCheck %s
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; If ARMBaseInstrInfo::AnalyzeBlocks returns the wrong value, which was possible
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; for blocks with indirect branches, the IfConverter could end up deleting
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; blocks that were the destinations of indirect branches, leaving branches to
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; nowhere.
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; <rdar://problem/14464830>
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define i32 @preserve_blocks(i32 %x) {
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; preserve_blocks:
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; CHECK: Block address taken
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; CHECK: movs r0, #2
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; CHECK: movs r0, #1
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; CHECK-NOT: Address of block that was removed by CodeGen
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entry:
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%c2 = icmp slt i32 %x, 3
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%blockaddr = select i1 %c2, i8* blockaddress(@preserve_blocks, %ibt1), i8* blockaddress(@preserve_blocks, %ibt2)
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%c1 = icmp eq i32 %x, 0
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br i1 %c1, label %pre_ib, label %nextblock
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nextblock:
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ret i32 3
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ibt1:
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ret i32 2
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ibt2:
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ret i32 1
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pre_ib:
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indirectbr i8* %blockaddr, [ label %ibt1, label %ibt2 ]
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}
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