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Fix FoldSingleEntryPHINodes to update memdep and AA when it deletes

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phi nodes.  It is called from MergeBlockIntoPredecessor which is 
called from GVN, which claims to preserve these.

I'm skeptical that this is the actual problem behind PR8954, but
this is a stab in the right direction.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@123222 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner
2011-01-11 08:13:40 +00:00
parent b298db7253
commit b5b7997fd0
3 changed files with 23 additions and 7 deletions
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22
lib/Transforms/Utils/BasicBlockUtils.cpp
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@@ -19,8 +19,9 @@
#include "llvm/Constant.h"
#include "llvm/Type.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/DominanceFrontier.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/MemoryDependenceAnalysis.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Transforms/Scalar.h"
@@ -63,12 +64,27 @@ void llvm::DeleteDeadBlock(BasicBlock *BB) {
/// any single-entry PHI nodes in it, fold them away. This handles the case
/// when all entries to the PHI nodes in a block are guaranteed equal, such as
/// when the block has exactly one predecessor.
void llvm::FoldSingleEntryPHINodes(BasicBlock *BB) {
void llvm::FoldSingleEntryPHINodes(BasicBlock *BB, Pass *P) {
if (!isa<PHINode>(BB->begin())) return;
AliasAnalysis *AA = 0;
MemoryDependenceAnalysis *MemDep = 0;
if (P) {
AA = P->getAnalysisIfAvailable<AliasAnalysis>();
MemDep = P->getAnalysisIfAvailable<MemoryDependenceAnalysis>();
}
while (PHINode *PN = dyn_cast<PHINode>(BB->begin())) {
if (PN->getIncomingValue(0) != PN)
PN->replaceAllUsesWith(PN->getIncomingValue(0));
else
PN->replaceAllUsesWith(UndefValue::get(PN->getType()));
if (MemDep)
MemDep->removeInstruction(PN); // Memdep updates AA itself.
else if (AA && isa<PointerType>(PN->getType()))
AA->deleteValue(PN);
PN->eraseFromParent();
}
}
@@ -132,7 +148,7 @@ bool llvm::MergeBlockIntoPredecessor(BasicBlock *BB, Pass *P) {
// Begin by getting rid of unneeded PHIs.
if (isa<PHINode>(BB->front()))
FoldSingleEntryPHINodes(BB);
FoldSingleEntryPHINodes(BB, P);
// Delete the unconditional branch from the predecessor...
PredBB->getInstList().pop_back();