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

llvm-svn: 73423
This commit is contained in:
Evan Cheng 2009-06-15 21:24:34 +00:00
parent ad0dba582f
commit b9bff5880a
2 changed files with 24 additions and 1 deletions
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13
llvm/lib/CodeGen/IfConversion.cpp
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@ -547,7 +547,11 @@ void IfConverter::ScanInstructions(BBInfo &BBI) {
// fallthrough.
if (!BBI.FalseBB)
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.
@ -663,6 +667,13 @@ IfConverter::BBInfo &IfConverter::AnalyzeBlock(MachineBasicBlock *BB,
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 &FalseBBI = AnalyzeBlock(BBI.FalseBB, Tokens);

12
llvm/test/CodeGen/ARM/ifcvt9.ll Normal file
View File

@ -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
}