Move the folding of gep null, 0, 0, 0 to a place where it can be shared and

enjoyed by all, fixing a fixme.  Add an assert


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@11505 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 15 insertions, 2 deletions

diff --git a/lib/VMCore/ConstantFold.cpp b/lib/VMCore/ConstantFold.cpp
index 28d671b898..39fac8d66a 100644
--- a/lib/VMCore/ConstantFold.cpp
+++ b/lib/VMCore/ConstantFold.cpp
@@ -927,8 +927,21 @@ Constant *llvm::ConstantFoldGetElementPtr(const Constant *C,
       (IdxList.size() == 1 && IdxList[0]->isNullValue()))
     return const_cast<Constant*>(C);
 
-  // TODO If C is null and all idx's are null, return null of the right type.
-
+  if (C->isNullValue()) {
+    bool isNull = true;
+    for (unsigned i = 0, e = IdxList.size(); i != e; ++i)
+      if (!IdxList[i]->isNullValue()) {
+        isNull = false;
+        break;
+      }
+    if (isNull) {
+      std::vector<Value*> VIdxList(IdxList.begin(), IdxList.end());
+      const Type *Ty = GetElementPtrInst::getIndexedType(C->getType(), VIdxList,
+                                                         true);
+      assert(Ty != 0 && "Invalid indices for GEP!");
+      return ConstantPointerNull::get(PointerType::get(Ty));
+    }
+  }
 
   if (ConstantExpr *CE = dyn_cast<ConstantExpr>(const_cast<Constant*>(C))) {
     // Combine Indices - If the source pointer to this getelementptr instruction