2 files changed, 53 insertions, 0 deletions
diff --git a/llvm/lib/IR/Metadata.cpp b/llvm/lib/IR/Metadata.cpp
index a32d25c92ae..ad943de88cc 100644
--- a/llvm/lib/IR/Metadata.cpp
+++ b/llvm/lib/IR/Metadata.cpp
@@ -16,6 +16,7 @@
 #include "SymbolTableListTraitsImpl.h"
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/SmallSet.h"
 #include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/StringMap.h"
 #include "llvm/IR/Instruction.h"
@@ -583,6 +584,50 @@ MDNode *Instruction::getMetadataImpl(StringRef Kind) const {
   return getMetadataImpl(getContext().getMDKindID(Kind));
 }
 
+void Instruction::dropUnknownMetadata(ArrayRef<unsigned> KnownIDs) {
+  SmallSet<unsigned, 5> KnownSet;
+  KnownSet.insert(KnownIDs.begin(), KnownIDs.end());
+
+  // Drop debug if needed
+  if (KnownSet.erase(LLVMContext::MD_dbg))
+    DbgLoc = DebugLoc();
+
+  if (!hasMetadataHashEntry())
+    return; // Nothing to remove!
+
+  DenseMap<const Instruction *, LLVMContextImpl::MDMapTy> &MetadataStore =
+      getContext().pImpl->MetadataStore;
+
+  if (KnownSet.empty()) {
+    // Just drop our entry at the store.
+    MetadataStore.erase(this);
+    setHasMetadataHashEntry(false);
+    return;
+  }
+
+  LLVMContextImpl::MDMapTy &Info = MetadataStore[this];
+  unsigned I;
+  unsigned E;
+  // Walk the array and drop any metadata we don't know.
+  for (I = 0, E = Info.size(); I != E;) {
+    if (KnownSet.count(Info[I].first)) {
+      ++I;
+      continue;
+    }
+
+    Info[I] = Info.back();
+    Info.pop_back();
+    --E;
+  }
+  assert(E == Info.size());
+
+  if (E == 0) {
+    // Drop our entry at the store.
+    MetadataStore.erase(this);
+    setHasMetadataHashEntry(false);
+  }
+}
+
 /// setMetadata - Set the metadata of of the specified kind to the specified
 /// node.  This updates/replaces metadata if already present, or removes it if
 /// Node is null.
diff --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
index 0401b9a7f7d..effc08edaa3 100644
--- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -2154,6 +2154,14 @@ bool llvm::FoldBranchToCommonDest(BranchInst *BI) {
     Instruction *NewBonus = 0;
     if (BonusInst) {
       NewBonus = BonusInst->clone();
+
+      // If we moved a load, we cannot any longer claim any knowledge about
+      // its potential value. The previous information might have been valid
+      // only given the branch precondition.
+      // For an analogous reason, we must also drop all the metadata whose
+      // semantics we don't understand.
+      NewBonus->dropUnknownMetadata(LLVMContext::MD_dbg);
+
       PredBlock->getInstList().insert(PBI, NewBonus);
       NewBonus->takeName(BonusInst);
       BonusInst->setName(BonusInst->getName()+".old");