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Generalize a special case to fix PR187 

llvm-svn: 10531
This commit is contained in:
Chris Lattner 2003-12-19 06:27:08 +00:00
parent 91daeb5431
commit 031a3f8cc7
1 changed files with 28 additions and 18 deletions
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44
llvm/lib/Transforms/Scalar/LoopSimplify.cpp
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@ -33,12 +33,12 @@
//===----------------------------------------------------------------------===// //===----------------------------------------------------------------------===//
#include "llvm/Transforms/Scalar.h" #include "llvm/Transforms/Scalar.h"
#include "llvm/Analysis/Dominators.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Function.h" #include "llvm/Function.h"
#include "llvm/iTerminators.h" #include "llvm/iTerminators.h"
#include "llvm/iPHINode.h" #include "llvm/iPHINode.h"
#include "llvm/Constant.h" #include "llvm/Constant.h"
#include "llvm/Analysis/Dominators.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Support/CFG.h" #include "llvm/Support/CFG.h"
#include "Support/SetOperations.h" #include "Support/SetOperations.h"
#include "Support/Statistic.h" #include "Support/Statistic.h"
@ -164,18 +164,22 @@ BasicBlock *LoopSimplify::SplitBlockPredecessors(BasicBlock *BB,
// incoming edges in BB into new PHI nodes in NewBB. // incoming edges in BB into new PHI nodes in NewBB.
// //
if (!Preds.empty()) { // Is the loop not obviously dead? if (!Preds.empty()) { // Is the loop not obviously dead?
if (Preds.size() == 1) { // Check to see if the values being merged into the new block need PHI
// No need to insert one operand PHI nodes! Instead, just update the // nodes. If so, insert them.
// incoming block ID's. for (BasicBlock::iterator I = BB->begin();
for (BasicBlock::iterator I = BB->begin(); PHINode *PN = dyn_cast<PHINode>(I); ++I) {
PHINode *PN = dyn_cast<PHINode>(I); ++I) {
unsigned i = PN->getBasicBlockIndex(Preds[0]);
PN->setIncomingBlock(i, NewBB);
}
} else {
for (BasicBlock::iterator I = BB->begin();
PHINode *PN = dyn_cast<PHINode>(I); ++I) {
// Check to see if all of the values coming in are the same. If so, we
// don't need to create a new PHI node.
Value *InVal = PN->getIncomingValueForBlock(Preds[0]);
for (unsigned i = 1, e = Preds.size(); i != e; ++i)
if (InVal != PN->getIncomingValueForBlock(Preds[i])) {
InVal = 0;
break;
}
// If the values coming into the block are not the same, we need a PHI.
if (InVal == 0) {
// Create the new PHI node, insert it into NewBB at the end of the block // Create the new PHI node, insert it into NewBB at the end of the block
PHINode *NewPHI = new PHINode(PN->getType(), PN->getName()+".ph", BI); PHINode *NewPHI = new PHINode(PN->getType(), PN->getName()+".ph", BI);
@ -184,11 +188,17 @@ BasicBlock *LoopSimplify::SplitBlockPredecessors(BasicBlock *BB,
Value *V = PN->removeIncomingValue(Preds[i]); Value *V = PN->removeIncomingValue(Preds[i]);
NewPHI->addIncoming(V, Preds[i]); NewPHI->addIncoming(V, Preds[i]);
} }
InVal = NewPHI;
// Add an incoming value to the PHI node in the loop for the preheader } else {
// edge. // Remove all of the edges coming into the PHI nodes from outside of the
PN->addIncoming(NewPHI, NewBB); // block.
for (unsigned i = 0, e = Preds.size(); i != e; ++i)
PN->removeIncomingValue(Preds[i], false);
} }
// Add an incoming value to the PHI node in the loop for the preheader
// edge.
PN->addIncoming(InVal, NewBB);
} }
// Now that the PHI nodes are updated, actually move the edges from // Now that the PHI nodes are updated, actually move the edges from