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Simplify some code, add the correct pred checks 

llvm-svn: 22613
This commit is contained in:
Chris Lattner 2005-08-03 00:38:27 +00:00
parent 982b75c061
commit 908036942c
1 changed files with 25 additions and 16 deletions
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41
llvm/lib/Transforms/Utils/SimplifyCFG.cpp
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@ -75,15 +75,29 @@ static void AddPredecessorToBlock(BasicBlock *Succ, BasicBlock *NewPred,
static bool CanPropagatePredecessorsForPHIs(BasicBlock *BB, BasicBlock *Succ) {
assert(*succ_begin(BB) == Succ && "Succ is not successor of BB!");
if (!isa<PHINode>(Succ->front()))
return true; // We can make the transformation, no problem.
// Check to see if one of the predecessors of BB is already a predecessor of
// Succ. If so, we cannot do the transformation if there are any PHI nodes
// with incompatible values coming in from the two edges!
//
if (!SafeToMergeTerminators(BB->getTerminator(), Succ->getTerminator()))
return false; // Cannot merge.
if (isa<PHINode>(Succ->front())) {
std::set<BasicBlock*> BBPreds(pred_begin(BB), pred_end(BB));
for (pred_iterator PI = pred_begin(Succ), PE = pred_end(Succ);\
PI != PE; ++PI)
if (std::find(BBPreds.begin(), BBPreds.end(), *PI) != BBPreds.end()) {
// Loop over all of the PHI nodes checking to see if there are
// incompatible values coming in.
for (BasicBlock::iterator I = Succ->begin(); isa<PHINode>(I); ++I) {
PHINode *PN = cast<PHINode>(I);
// Loop up the entries in the PHI node for BB and for *PI if the
// values coming in are non-equal, we cannot merge these two blocks
// (instead we should insert a conditional move or something, then
// merge the blocks).
if (PN->getIncomingValueForBlock(BB) !=
PN->getIncomingValueForBlock(*PI))
return false; // Values are not equal...
}
}
}
return true;
}
@ -114,8 +128,8 @@ static bool TryToSimplifyUncondBranchFromEmptyBlock(BasicBlock *BB,
Value *OldVal = PN->removeIncomingValue(BB, false);
assert(OldVal && "No entry in PHI for Pred BB!");
// If this incoming value is one of the PHI nodes in BB, the new entries in
// the PHI node are the entries from the old PHI.
// If this incoming value is one of the PHI nodes in BB, the new entries
// in the PHI node are the entries from the old PHI.
if (isa<PHINode>(OldVal) && cast<PHINode>(OldVal)->getParent() == BB) {
PHINode *OldValPN = cast<PHINode>(OldVal);
for (unsigned i = 0, e = OldValPN->getNumIncomingValues(); i != e; ++i)
@ -138,15 +152,10 @@ static bool TryToSimplifyUncondBranchFromEmptyBlock(BasicBlock *BB,
// Move all PHI nodes in BB to Succ if they are alive, otherwise
// delete them.
while (PHINode *PN = dyn_cast<PHINode>(&BB->front()))
if (PN->use_empty() /*|| Succ->getSinglePredecessor() == 0*/) {
// We can only move the PHI node into Succ if BB dominates Succ.
// Since BB only has a single successor (Succ), the PHI nodes
// will dominate Succ, unless Succ has multiple predecessors. In
// this case, the PHIs are either dead, or have references in dead
// blocks. In either case, we can just remove them.
if (!PN->use_empty()) // Uses in dead block?
PN->replaceAllUsesWith(UndefValue::get(PN->getType()));
PN->eraseFromParent(); // Nuke instruction.
if (PN->use_empty()) {
// Just remove the dead phi. This happens if Succ's PHIs were the only
// users of the PHI nodes.
PN->eraseFromParent();
} else {
// The instruction is alive, so this means that Succ must have
// *ONLY* had BB as a predecessor, and the PHI node is still valid