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SDISel should not optimize a unconditional branch following a conditional branch

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when the unconditional branch destination is the fallthrough block. The
canonicalization makes it easier to allow optimizations on DAGs to invert
conditional branches. The branch folding pass (and AnalyzeBranch) will clean up
the unnecessary unconditional branches later.

This is one of the patches leading up to disabling codegen prepare critical edge
splitting.

llvm-svn: 114630
This commit is contained in:
Evan Cheng 2010-09-23 06:51:55 +00:00
parent f670bff621
commit 3866797d9a
1 changed files with 5 additions and 4 deletions
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9
lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
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@ -1503,10 +1503,11 @@ void SelectionDAGBuilder::visitSwitchCase(CaseBlock &CB,
MVT::Other, getControlRoot(), Cond,
DAG.getBasicBlock(CB.TrueBB));
// Insert the false branch.
if (CB.FalseBB != NextBlock)
BrCond = DAG.getNode(ISD::BR, dl, MVT::Other, BrCond,
DAG.getBasicBlock(CB.FalseBB));
// Insert the false branch. Do this even if it's a fall through branch,
// this makes it easier to do DAG optimizations which require inverting
// the branch condition.
BrCond = DAG.getNode(ISD::BR, dl, MVT::Other, BrCond,
DAG.getBasicBlock(CB.FalseBB));
DAG.setRoot(BrCond);
}