[llvm-commits] [llvm] r111922 - /llvm/trunk/lib/Transforms/Utils/ValueMapper.cpp

[Dan Gohman]

Author: djg
Date: Tue Aug 24 12:10:10 2010
New Revision: 111922

URL: http://llvm.org/viewvc/llvm-project?rev=111922&view=rev
Log:
MapValue support for MDNodes. This is similar to r109117, except
that it avoids a lot of unnecessary cloning by avoiding remapping
MDNode cycles when none of the nodes in the cycle actually need to
be remapped. Also it uses the new temporary MDNode mechanism.

Modified:
    llvm/trunk/lib/Transforms/Utils/ValueMapper.cpp

Modified: llvm/trunk/lib/Transforms/Utils/ValueMapper.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/ValueMapper.cpp?rev=111922&r1=111921&r2=111922&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/ValueMapper.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/ValueMapper.cpp Tue Aug 24 12:10:10 2010
@@ -27,17 +27,36 @@
   // NOTE: VMSlot can be invalidated by any reference to VM, which can grow the
   // DenseMap.  This includes any recursive calls to MapValue.
 
-  // 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()))
+  // 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))
     return VMSlot = const_cast<Value*>(V);
 
   if (const MDNode *MD = dyn_cast<MDNode>(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());
+    // 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);
   }
 
   Constant *C = const_cast<Constant*>(dyn_cast<Constant>(V));