1 files changed, 38 insertions, 37 deletions

diff --git a/lib/Transforms/IPO/IPConstantPropagation.cpp b/lib/Transforms/IPO/IPConstantPropagation.cpp
index af541d155254..916135e33cd5 100644
--- a/lib/Transforms/IPO/IPConstantPropagation.cpp
+++ b/lib/Transforms/IPO/IPConstantPropagation.cpp
@@ -41,44 +41,14 @@ namespace {
     }
 
     bool runOnModule(Module &M) override;
-  private:
-    bool PropagateConstantsIntoArguments(Function &F);
-    bool PropagateConstantReturn(Function &F);
   };
 }
 
-char IPCP::ID = 0;
-INITIALIZE_PASS(IPCP, "ipconstprop",
-                "Interprocedural constant propagation", false, false)
-
-ModulePass *llvm::createIPConstantPropagationPass() { return new IPCP(); }
-
-bool IPCP::runOnModule(Module &M) {
-  bool Changed = false;
-  bool LocalChange = true;
-
-  // FIXME: instead of using smart algorithms, we just iterate until we stop
-  // making changes.
-  while (LocalChange) {
-    LocalChange = false;
-    for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
-      if (!I->isDeclaration()) {
-        // Delete any klingons.
-        I->removeDeadConstantUsers();
-        if (I->hasLocalLinkage())
-          LocalChange |= PropagateConstantsIntoArguments(*I);
-        Changed |= PropagateConstantReturn(*I);
-      }
-    Changed |= LocalChange;
-  }
-  return Changed;
-}
-
 /// PropagateConstantsIntoArguments - Look at all uses of the specified
 /// function.  If all uses are direct call sites, and all pass a particular
 /// constant in for an argument, propagate that constant in as the argument.
 ///
-bool IPCP::PropagateConstantsIntoArguments(Function &F) {
+static bool PropagateConstantsIntoArguments(Function &F) {
   if (F.arg_empty() || F.use_empty()) return false; // No arguments? Early exit.
 
   // For each argument, keep track of its constant value and whether it is a
@@ -157,13 +127,14 @@ bool IPCP::PropagateConstantsIntoArguments(Function &F) {
 // Additionally if a function always returns one of its arguments directly,
 // callers will be updated to use the value they pass in directly instead of
 // using the return value.
-bool IPCP::PropagateConstantReturn(Function &F) {
+static bool PropagateConstantReturn(Function &F) {
   if (F.getReturnType()->isVoidTy())
     return false; // No return value.
 
-  // If this function could be overridden later in the link stage, we can't
-  // propagate information about its results into callers.
-  if (F.mayBeOverridden())
+  // We can infer and propagate the return value only when we know that the
+  // definition we'll get at link time is *exactly* the definition we see now.
+  // For more details, see GlobalValue::mayBeDerefined.
+  if (!F.isDefinitionExact())
     return false;
     
   // Check to see if this function returns a constant.
@@ -176,8 +147,8 @@ bool IPCP::PropagateConstantReturn(Function &F) {
     RetVals.push_back(UndefValue::get(F.getReturnType()));
 
   unsigned NumNonConstant = 0;
-  for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
-    if (ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator())) {
+  for (BasicBlock &BB : F)
+    if (ReturnInst *RI = dyn_cast<ReturnInst>(BB.getTerminator())) {
       for (unsigned i = 0, e = RetVals.size(); i != e; ++i) {
         // Already found conflicting return values?
         Value *RV = RetVals[i];
@@ -277,3 +248,33 @@ bool IPCP::PropagateConstantReturn(Function &F) {
   if (MadeChange) ++NumReturnValProped;
   return MadeChange;
 }
+
+char IPCP::ID = 0;
+INITIALIZE_PASS(IPCP, "ipconstprop",
+                "Interprocedural constant propagation", false, false)
+
+ModulePass *llvm::createIPConstantPropagationPass() { return new IPCP(); }
+
+bool IPCP::runOnModule(Module &M) {
+  if (skipModule(M))
+    return false;
+
+  bool Changed = false;
+  bool LocalChange = true;
+
+  // FIXME: instead of using smart algorithms, we just iterate until we stop
+  // making changes.
+  while (LocalChange) {
+    LocalChange = false;
+    for (Function &F : M)
+      if (!F.isDeclaration()) {
+        // Delete any klingons.
+        F.removeDeadConstantUsers();
+        if (F.hasLocalLinkage())
+          LocalChange |= PropagateConstantsIntoArguments(F);
+        Changed |= PropagateConstantReturn(F);
+      }
+    Changed |= LocalChange;
+  }
+  return Changed;
+}