Revert r111922, "MapValue support for MDNodes. This is similar to r109117,

except ...", it is causing *massive* performance regressions when building Clang
with itself (-O3 -g).

llvm-svn: 112158

1 files changed, 8 insertions, 27 deletions

diff --git a/llvm/lib/Transforms/Utils/ValueMapper.cpp b/llvm/lib/Transforms/Utils/ValueMapper.cpp
index df11cbbcb27..20e7f79b87d 100644
--- a/llvm/lib/Transforms/Utils/ValueMapper.cpp
+++ b/llvm/lib/Transforms/Utils/ValueMapper.cpp
@@ -27,36 +27,17 @@ Value *llvm::MapValue(const Value *V, ValueToValueMapTy &VM) {
   // NOTE: VMSlot can be invalidated by any reference to VM, which can grow the
   // DenseMap.  This includes any recursive calls to MapValue.
 
-  // Global values do not need to be seeded into the VM if they
-  // are using the identity mapping.
-  if (isa<GlobalValue>(V) || isa<InlineAsm>(V) || isa<MDString>(V))
+  // Global values and non-function-local metadata do not need to be seeded into
+  // the VM if they are using the identity mapping.
+  if (isa<GlobalValue>(V) || isa<InlineAsm>(V) || isa<MDString>(V) ||
+      (isa<MDNode>(V) && !cast<MDNode>(V)->isFunctionLocal()))
     return VMSlot = const_cast<Value*>(V);
 
   if (const MDNode *MD = dyn_cast<MDNode>(V)) {
-    // Start by assuming that we'll use the identity mapping.
-    VMSlot = const_cast<Value*>(V);
-
-    // Check all operands to see if any need to be remapped.
-    for (unsigned i = 0, e = MD->getNumOperands(); i != e; ++i) {
-      Value *OP = MD->getOperand(i);
-      if (!OP || MapValue(OP, VM) == OP) continue;
-
-      // Ok, at least one operand needs remapping.
-      MDNode *Dummy = MDNode::getTemporary(V->getContext(), 0, 0);
-      VM[V] = Dummy;
-      SmallVector<Value*, 4> Elts;
-      Elts.reserve(MD->getNumOperands());
-      for (i = 0; i != e; ++i)
-        Elts.push_back(MD->getOperand(i) ? 
-                       MapValue(MD->getOperand(i), VM) : 0);
-      MDNode *NewMD = MDNode::get(V->getContext(), Elts.data(), Elts.size());
-      Dummy->replaceAllUsesWith(NewMD);
-      MDNode::deleteTemporary(Dummy);
-      return VM[V] = NewMD;
-    }
-
-    // No operands needed remapping; keep the identity map.
-    return const_cast<Value*>(V);
+    SmallVector<Value*, 4> Elts;
+    for (unsigned i = 0, e = MD->getNumOperands(); i != e; ++i)
+      Elts.push_back(MD->getOperand(i) ? MapValue(MD->getOperand(i), VM) : 0);
+    return VM[V] = MDNode::get(V->getContext(), Elts.data(), Elts.size());
   }
 
   Constant *C = const_cast<Constant*>(dyn_cast<Constant>(V));