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Factor MergeBlockIntoPredecessor out into BasicBlockUtils.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@53705 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Owen Anderson 2008-07-17 00:01:40 +00:00
parent 413907000e
commit b31b06d04b
3 changed files with 60 additions and 51 deletions
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4
include/llvm/Transforms/Utils/BasicBlockUtils.h
View File

@ -25,6 +25,10 @@ namespace llvm {
class Instruction;
class Pass;
/// MergeBlockIntoPredecessor - Attempts to merge a block into its predecessor,
/// if possible. The return value indicates success or failure.
bool MergeBlockIntoPredecessor(BasicBlock* BB, Pass* P);
// ReplaceInstWithValue - Replace all uses of an instruction (specified by BI)
// with a value, then remove and delete the original instruction.
//

55
lib/Transforms/Scalar/GVN.cpp
View File

@ -1125,7 +1125,10 @@ bool GVN::runOnFunction(Function& F) {
for (Function::iterator FI = F.begin(), FE = F.end(); FI != FE; ) {
BasicBlock* BB = FI;
++FI;
changed |= mergeBlockIntoPredecessor(BB);
bool removedBlock = MergeBlockIntoPredecessor(BB, this);
if (removedBlock) NumGVNBlocks++;
changed |= removedBlock;
}
while (shouldContinue) {
@ -1336,56 +1339,6 @@ bool GVN::performPRE(Function& F) {
return changed;
}
// mergeBlockIntoPredecessor - If this block is the only successor
// of its predecessor, and the edge is non-critical,
// fold it into that predecessor.
bool GVN::mergeBlockIntoPredecessor(BasicBlock* BB) {
// Can't merge the entry block.
if (pred_begin(BB) == pred_end(BB)) return false;
// Can't merge if there are multiple preds.
if (++pred_begin(BB) != pred_end(BB)) return false;
BasicBlock* PredBB = *pred_begin(BB);
// Can't merge if the edge is critical.
if (PredBB->getTerminator()->getNumSuccessors() != 1) return false;
// Begin by getting rid of unneeded PHIs.
while (PHINode *PN = dyn_cast<PHINode>(&BB->front())) {
PN->replaceAllUsesWith(PN->getIncomingValue(0));
BB->getInstList().pop_front(); // Delete the phi node...
}
// Delete the unconditional branch from the predecessor...
PredBB->getInstList().pop_back();
// Move all definitions in the successor to the predecessor...
PredBB->getInstList().splice(PredBB->end(), BB->getInstList());
// Make all PHI nodes that referred to BB now refer to Pred as their
// source...
BB->replaceAllUsesWith(PredBB);
// Finally, erase the old block and update dominator info.
DominatorTree& DT = getAnalysis<DominatorTree>();
DomTreeNode* DTN = DT[BB];
DomTreeNode* PredDTN = DT[PredBB];
if (DTN) {
SmallPtrSet<DomTreeNode*, 8> Children(DTN->begin(), DTN->end());
for (SmallPtrSet<DomTreeNode*, 8>::iterator DI = Children.begin(),
DE = Children.end(); DI != DE; ++DI)
DT.changeImmediateDominator(*DI, PredDTN);
DT.eraseNode(BB);
}
BB->eraseFromParent();
NumGVNBlocks++;
return true;
}
// iterateOnFunction - Executes one iteration of GVN
bool GVN::iterateOnFunction(Function &F) {
// Clean out global sets from any previous functions

52
lib/Transforms/Utils/BasicBlockUtils.cpp
View File

@ -23,6 +23,58 @@
#include <algorithm>
using namespace llvm;
/// MergeBlockIntoPredecessor - Attempts to merge a block into its predecessor,
/// if possible. The return value indicates success or failure.
bool llvm::MergeBlockIntoPredecessor(BasicBlock* BB, Pass* P) {
// Can't merge the entry block.
if (pred_begin(BB) == pred_end(BB)) return false;
// Can't merge if there are multiple preds.
if (++pred_begin(BB) != pred_end(BB)) return false;
BasicBlock* PredBB = *pred_begin(BB);
// Can't merge if the edge is critical.
if (PredBB->getTerminator()->getNumSuccessors() != 1) return false;
// Begin by getting rid of unneeded PHIs.
while (PHINode *PN = dyn_cast<PHINode>(&BB->front())) {
PN->replaceAllUsesWith(PN->getIncomingValue(0));
BB->getInstList().pop_front(); // Delete the phi node...
}
// Delete the unconditional branch from the predecessor...
PredBB->getInstList().pop_back();
// Move all definitions in the successor to the predecessor...
PredBB->getInstList().splice(PredBB->end(), BB->getInstList());
// Make all PHI nodes that referred to BB now refer to Pred as their
// source...
BB->replaceAllUsesWith(PredBB);
// Finally, erase the old block and update dominator info.
if (P) {
if (DominatorTree* DT = P->getAnalysisToUpdate<DominatorTree>()) {
DomTreeNode* DTN = DT->getNode(BB);
DomTreeNode* PredDTN = DT->getNode(PredBB);
if (DTN) {
SmallPtrSet<DomTreeNode*, 8> Children(DTN->begin(), DTN->end());
for (SmallPtrSet<DomTreeNode*, 8>::iterator DI = Children.begin(),
DE = Children.end(); DI != DE; ++DI)
DT->changeImmediateDominator(*DI, PredDTN);
DT->eraseNode(BB);
}
}
}
BB->eraseFromParent();
return true;
}
/// ReplaceInstWithValue - Replace all uses of an instruction (specified by BI)
/// with a value, then remove and delete the original instruction.
///