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Teach cee to propagate through switch statements. This implements 

Transforms/CorrelatedExprs/switch.ll

Patch contributed by Eric Kidd!

llvm-svn: 26872
This commit is contained in:
Chris Lattner 2006-03-19 19:37:24 +00:00
parent 2a028e2f95
commit d783c76c18
1 changed files with 21 additions and 1 deletions
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22
llvm/lib/Transforms/Scalar/CorrelatedExprs.cpp
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@ -267,6 +267,7 @@ namespace {
const std::vector<BasicBlock*> &RegionExitBlocks);
void PropagateBranchInfo(BranchInst *BI);
void PropagateSwitchInfo(SwitchInst *SI);
void PropagateEquality(Value *Op0, Value *Op1, RegionInfo &RI);
void PropagateRelation(Instruction::BinaryOps Opcode, Value *Op0,
Value *Op1, RegionInfo &RI);
@ -360,9 +361,12 @@ bool CEE::TransformRegion(BasicBlock *BB, std::set<BasicBlock*> &VisitedBlocks){
// Now that all of our successors have information if they deserve it,
// propagate any information our terminator instruction finds to our
// successors.
if (BranchInst *BI = dyn_cast<BranchInst>(TI))
if (BranchInst *BI = dyn_cast<BranchInst>(TI)) {
if (BI->isConditional())
PropagateBranchInfo(BI);
} else if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) {
PropagateSwitchInfo(SI);
}
// If this is a branch to a block outside our region that simply performs
// another conditional branch, one whose outcome is known inside of this
@ -794,6 +798,22 @@ void CEE::PropagateBranchInfo(BranchInst *BI) {
}
// PropagateSwitchInfo - We need to propagate the value tested by the
// switch statement through each case block.
//
void CEE::PropagateSwitchInfo(SwitchInst *SI) {
// Propagate information down each of our non-default case labels. We
// don't yet propagate information down the default label, because a
// potentially large number of inequality constraints provide less
// benefit per unit work than a single equality constraint.
//
Value *cond = SI->getCondition();
for (unsigned i = 1; i < SI->getNumSuccessors(); ++i)
PropagateEquality(cond, SI->getSuccessorValue(i),
getRegionInfo(SI->getSuccessor(i)));
}
// PropagateEquality - If we discover that two values are equal to each other in
// a specified region, propagate this knowledge recursively.
//