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move 'MergeBlocksIntoPredecessor' call earlier. Use

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getSinglePredecessor to simplify code.

llvm-svn: 121683
This commit is contained in:
Chris Lattner 2010-12-13 05:10:48 +00:00
parent c331eb8e1e
commit 80f8577d74
1 changed files with 9 additions and 20 deletions
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29
lib/Transforms/Utils/SimplifyCFG.cpp
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@ -1957,6 +1957,13 @@ bool SimplifyCFGOpt::run(BasicBlock *BB) {
// Check for and eliminate duplicate PHI nodes in this block.
Changed |= EliminateDuplicatePHINodes(BB);
// Merge basic blocks into their predecessor if there is only one distinct
// pred, and if there is only one distinct successor of the predecessor, and
// if there are no PHI nodes.
//
if (MergeBlockIntoPredecessor(BB))
return true;
// If there is a trivial two-entry PHI node in this basic block, and we can
// eliminate it, do so now.
if (PHINode *PN = dyn_cast<PHINode>(BB->begin()))
@ -2309,33 +2316,15 @@ bool SimplifyCFGOpt::run(BasicBlock *BB) {
}
}
// Merge basic blocks into their predecessor if there is only one distinct
// pred, and if there is only one distinct successor of the predecessor, and
// if there are no PHI nodes.
//
if (MergeBlockIntoPredecessor(BB))
return true;
// Otherwise, if this block only has a single predecessor, and if that block
// is a conditional branch, see if we can hoist any code from this block up
// into our predecessor.
pred_iterator PI(pred_begin(BB)), PE(pred_end(BB));
BasicBlock *OnlyPred = 0;
for (; PI != PE; ++PI) { // Search all predecessors, see if they are all same
if (!OnlyPred)
OnlyPred = *PI;
else if (*PI != OnlyPred) {
OnlyPred = 0; // There are multiple different predecessors...
break;
}
}
if (OnlyPred) {
if (BasicBlock *OnlyPred = BB->getSinglePredecessor()) {
BranchInst *BI = dyn_cast<BranchInst>(OnlyPred->getTerminator());
if (BI && BI->isConditional()) {
// Get the other block.
BasicBlock *OtherBB = BI->getSuccessor(BI->getSuccessor(0) == BB);
PI = pred_begin(OtherBB);
pred_iterator PI = pred_begin(OtherBB);
++PI;
if (PI == pred_end(OtherBB)) {