Introduce ImmutableCallSite, useful for contexts where no mutation

[oota-llvm.git] / lib / Transforms / Scalar / SCCP.cpp

diff --git a/lib/Transforms/Scalar/SCCP.cpp b/lib/Transforms/Scalar/SCCP.cpp
index 8d06690f2a4747328a0bf92886643b0789982c2d..546b7b6cc292081fd3436474a46d19c7e2d5c13e 100644 (file)
--- a/lib/Transforms/Scalar/SCCP.cpp
+++ b/lib/Transforms/Scalar/SCCP.cpp
@@ -1705,28 +1705,31 @@ ModulePass *llvm::createIPSCCPPass() {
 }
 
 
-static bool AddressIsTaken(GlobalValue *GV) {
+static bool AddressIsTaken(const GlobalValue *GV) {
   // Delete any dead constantexpr klingons.
   GV->removeDeadConstantUsers();
 
-  for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end();
-       UI != E; ++UI)
-    if (StoreInst *SI = dyn_cast<StoreInst>(*UI)) {
+  for (Value::const_use_iterator UI = GV->use_begin(), E = GV->use_end();
+       UI != E; ++UI) {
+    const User *U = *UI;
+    if (const StoreInst *SI = dyn_cast<StoreInst>(U)) {
       if (SI->getOperand(0) == GV || SI->isVolatile())
         return true;  // Storing addr of GV.
-    } else if (isa<InvokeInst>(*UI) || isa<CallInst>(*UI)) {
+    } else if (isa<InvokeInst>(U) || isa<CallInst>(U)) {
       // Make sure we are calling the function, not passing the address.
-      if (UI.getOperandNo() != 0)
+      ImmutableCallSite CS(cast<Instruction>(U));
+      if (!CS.isCallee(UI))
         return true;
-    } else if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) {
+    } else if (const LoadInst *LI = dyn_cast<LoadInst>(U)) {
       if (LI->isVolatile())
         return true;
-    } else if (isa<BlockAddress>(*UI)) {
+    } else if (isa<BlockAddress>(U)) {
       // blockaddress doesn't take the address of the function, it takes addr
       // of label.
     } else {
       return true;
     }
+  }
   return false;
 }
 
@@ -1918,6 +1921,14 @@ bool IPSCCP::runOnModule(Module &M) {
   // all call uses with the inferred value.  This means we don't need to bother
   // actually returning anything from the function.  Replace all return
   // instructions with return undef.
+  //
+  // Do this in two stages: first identify the functions we should process, then
+  // actually zap their returns.  This is important because we can only do this
+  // if the address of the function isn't taken.  In cases where a return is the
+  // last use of a function, the order of processing functions would affect
+  // whether other functions are optimizable.
+  SmallVector<ReturnInst*, 8> ReturnsToZap;
+  
   // TODO: Process multiple value ret instructions also.
   const DenseMap<Function*, LatticeVal> &RV = Solver.getTrackedRetVals();
   for (DenseMap<Function*, LatticeVal>::const_iterator I = RV.begin(),
@@ -1933,7 +1944,13 @@ bool IPSCCP::runOnModule(Module &M) {
     for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB)
       if (ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator()))
         if (!isa<UndefValue>(RI->getOperand(0)))
-          RI->setOperand(0, UndefValue::get(F->getReturnType()));
+          ReturnsToZap.push_back(RI);
+  }
+
+  // Zap all returns which we've identified as zap to change.
+  for (unsigned i = 0, e = ReturnsToZap.size(); i != e; ++i) {
+    Function *F = ReturnsToZap[i]->getParent()->getParent();
+    ReturnsToZap[i]->setOperand(0, UndefValue::get(F->getReturnType()));
   }
     
   // If we infered constant or undef values for globals variables, we can delete