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ifcvt should ignore cfg where true and false successors are the same.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@73423 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Evan Cheng
2009-06-15 21:24:34 +00:00
parent 675860758e
commit 2077e18caf
2 changed files with 24 additions and 1 deletions
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13
lib/CodeGen/IfConversion.cpp
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@@ -547,7 +547,11 @@ void IfConverter::ScanInstructions(BBInfo &BBI) {
// fallthrough. // fallthrough.
if (!BBI.FalseBB) if (!BBI.FalseBB)
BBI.FalseBB = findFalseBlock(BBI.BB, BBI.TrueBB); BBI.FalseBB = findFalseBlock(BBI.BB, BBI.TrueBB);
assert(BBI.FalseBB && "Expected to find the fallthrough block!"); if (!BBI.FalseBB) {
// Malformed bcc? True and false blocks are the same?
BBI.IsUnpredicable = true;
return;
}
} }
// Then scan all the instructions. // Then scan all the instructions.
@@ -663,6 +667,13 @@ IfConverter::BBInfo &IfConverter::AnalyzeBlock(MachineBasicBlock *BB,
return BBI; return BBI;
} }
// Do not ifcvt if true and false fallthrough blocks are the same.
if (!BBI.FalseBB) {
BBI.IsBeingAnalyzed = false;
BBI.IsAnalyzed = true;
return BBI;
}
BBInfo &TrueBBI = AnalyzeBlock(BBI.TrueBB, Tokens); BBInfo &TrueBBI = AnalyzeBlock(BBI.TrueBB, Tokens);
BBInfo &FalseBBI = AnalyzeBlock(BBI.FalseBB, Tokens); BBInfo &FalseBBI = AnalyzeBlock(BBI.FalseBB, Tokens);

12
test/CodeGen/ARM/ifcvt9.ll Normal file
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@@ -0,0 +1,12 @@
; RUN: llvm-as < %s | llc -march=arm
define fastcc void @t() nounwind {
entry:
br i1 undef, label %bb.i.i3, label %growMapping.exit
bb.i.i3: ; preds = %entry
unreachable
growMapping.exit: ; preds = %entry
unreachable
}