Fix FoldSingleEntryPHINodes to update memdep and AA when it deletes
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
diff --git a/lib/Transforms/Utils/BasicBlockUtils.cpp b/lib/Transforms/Utils/BasicBlockUtils.cpp
index 3daa45c..40d33d1 100644
--- a/lib/Transforms/Utils/BasicBlockUtils.cpp
+++ b/lib/Transforms/Utils/BasicBlockUtils.cpp
@@ -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 @@
/// 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 @@
// 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();