Avoid doing pointless work. Amazingly, this makes us go faster.

Running the inliner on 252.eon used to take 48.4763s, now it takes 14.4148s.

In release mode, it went from taking 25.8741s to taking 11.5712s.

This also fixes a FIXME.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@8890 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 5 insertions, 8 deletions

diff --git a/lib/Transforms/Utils/InlineFunction.cpp b/lib/Transforms/Utils/InlineFunction.cpp
index 22377b759c..01ffb253e4 100644
--- a/lib/Transforms/Utils/InlineFunction.cpp
+++ b/lib/Transforms/Utils/InlineFunction.cpp
@@ -124,14 +124,6 @@ bool InlineFunction(CallSite CS) {
   // Make a vector to capture the return instructions in the cloned function...
   std::vector<ReturnInst*> Returns;
 
-  // Populate the value map with all of the globals in the program.
-  // FIXME: This should be the default for CloneFunctionInto!
-  Module &M = *Caller->getParent();
-  for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
-    ValueMap[I] = I;
-  for (Module::giterator I = M.gbegin(), E = M.gend(); I != E; ++I)
-    ValueMap[I] = I;
-
   // Do all of the hard part of cloning the callee into the caller...
   CloneFunctionInto(Caller, CalledFunc, ValueMap, Returns, ".i");
 
diff --git a/lib/Transforms/Utils/ValueMapper.cpp b/lib/Transforms/Utils/ValueMapper.cpp
index 484765a7e2..d79c21f474 100644
--- a/lib/Transforms/Utils/ValueMapper.cpp
+++ b/lib/Transforms/Utils/ValueMapper.cpp
@@ -13,6 +13,11 @@ Value *MapValue(const Value *V, std::map<const Value*, Value*> &VM) {
   Value *&VMSlot = VM[V];
   if (VMSlot) return VMSlot;      // Does it exist in the map yet?
   
+  // Global values do not need to be seeded into the ValueMap if they are using
+  // the identity mapping.
+  if (isa<GlobalValue>(V))
+    return VMSlot = const_cast<Value*>(V);
+
   if (Constant *C = const_cast<Constant*>(dyn_cast<Constant>(V))) {
     if (isa<ConstantIntegral>(C) || isa<ConstantFP>(C) ||
         isa<ConstantPointerNull>(C))