Explicitely track if any arguments or return values were removed in

DeadArgumentElimination and assert that the function type does not change if
nothing was changed. This should catch subtle changes in function type that are
not intended.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@52536 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 10 insertions, 1 deletions

diff --git a/lib/Transforms/IPO/DeadArgumentElimination.cpp b/lib/Transforms/IPO/DeadArgumentElimination.cpp
index 36be6f8..6f00c89 100644
--- a/lib/Transforms/IPO/DeadArgumentElimination.cpp
+++ b/lib/Transforms/IPO/DeadArgumentElimination.cpp
@@ -568,6 +568,8 @@ bool DAE::RemoveDeadStuffFromFunction(Function *F) {
   const Type *RetTy = FTy->getReturnType();
   const Type *NRetTy;
   unsigned RetCount = NumRetVals(F);
+  // Explicitely track if anything changed, for debugging
+  bool Changed = false;
   // -1 means unused, other numbers are the new index
   SmallVector<int, 5> NewRetIdxs(RetCount, -1);
   std::vector<const Type*> RetTypes;
@@ -582,7 +584,8 @@ bool DAE::RemoveDeadStuffFromFunction(Function *F) {
           NewRetIdxs[i] = RetTypes.size() - 1;
         } else {
           ++NumRetValsEliminated;
-        DOUT << "DAE - Removing return value " << i << " from " << F->getNameStart() << "\n";
+          DOUT << "DAE - Removing return value " << i << " from " << F->getNameStart() << "\n";
+          Changed = true;
         }
       }
     else
@@ -593,6 +596,7 @@ bool DAE::RemoveDeadStuffFromFunction(Function *F) {
       } else {
         DOUT << "DAE - Removing return value from " << F->getNameStart() << "\n";
         ++NumRetValsEliminated;
+        Changed = true;
       } 
     if (RetTypes.size() == 0)
       // No return types? Make it void
@@ -632,6 +636,7 @@ bool DAE::RemoveDeadStuffFromFunction(Function *F) {
     } else {
       ++NumArgumentsEliminated;
       DOUT << "DAE - Removing argument " << i << " (" << I->getNameStart() << ") from " << F->getNameStart() << "\n";
+      Changed = true;
     }
   }
 
@@ -657,6 +662,10 @@ bool DAE::RemoveDeadStuffFromFunction(Function *F) {
   if (NFTy == FTy)
     return false;
 
+  // The function type is only allowed to be different if we actually left out
+  // an argument or return value
+  assert(Changed && "Function type changed while no arguments or retrurn values were removed!");
+
   // Create the new function body and insert it into the module...
   Function *NF = Function::Create(NFTy, F->getLinkage());
   NF->copyAttributesFrom(F);