From 9cb6ec26b3041ff4879579fd9ecee48b616154d8 Mon Sep 17 00:00:00 2001
From: Matthijs Kooijman <matthijs@stdin.nl>
Date: Fri, 20 Jun 2008 14:28:52 +0000
Subject: [PATCH] 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
---
 lib/Transforms/IPO/DeadArgumentElimination.cpp | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/lib/Transforms/IPO/DeadArgumentElimination.cpp b/lib/Transforms/IPO/DeadArgumentElimination.cpp
index 36be6f8f4dd..6f00c89bf56 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);