From 04b60fe5ad29fa2f3e1daed41cc9a5bc1eebc81c Mon Sep 17 00:00:00 2001
From: Chris Lattner <sabre@nondot.org>
Date: Mon, 16 Feb 2004 20:46:13 +0000
Subject: [PATCH] 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

llvm-svn: 11505
---
 llvm/lib/VMCore/ConstantFolding.cpp | 17 +++++++++++++++--
 llvm/lib/VMCore/Constants.cpp       | 17 +++++------------
 2 files changed, 20 insertions(+), 14 deletions(-)

diff --git a/llvm/lib/VMCore/ConstantFolding.cpp b/llvm/lib/VMCore/ConstantFolding.cpp
index 28d671b898c9..39fac8d66a4a 100644
--- a/llvm/lib/VMCore/ConstantFolding.cpp
+++ b/llvm/lib/VMCore/ConstantFolding.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
diff --git a/llvm/lib/VMCore/Constants.cpp b/llvm/lib/VMCore/Constants.cpp
index dac23aea55c0..5a617fad9ae5 100644
--- a/llvm/lib/VMCore/Constants.cpp
+++ b/llvm/lib/VMCore/Constants.cpp
@@ -1081,11 +1081,15 @@ Constant *ConstantExpr::getShiftTy(const Type *ReqTy, unsigned Opcode,
 
 Constant *ConstantExpr::getGetElementPtrTy(const Type *ReqTy, Constant *C,
                                         const std::vector<Constant*> &IdxList) {
+  assert(GetElementPtrInst::getIndexedType(C->getType(),
+                   std::vector<Value*>(IdxList.begin(), IdxList.end()), true) &&
+         "GEP indices invalid!");
+
   if (Constant *FC = ConstantFoldGetElementPtr(C, IdxList))
     return FC;          // Fold a few common cases...
+
   assert(isa<PointerType>(C->getType()) &&
          "Non-pointer type for constant GetElementPtr expression");
-
   // Look up the constant in the table first to ensure uniqueness
   std::vector<Constant*> argVec(1, C);
   argVec.insert(argVec.end(), IdxList.begin(), IdxList.end());
@@ -1101,17 +1105,6 @@ Constant *ConstantExpr::getGetElementPtr(Constant *C,
   const Type *Ty = GetElementPtrInst::getIndexedType(C->getType(), VIdxList,
                                                      true);
   assert(Ty && "GEP indices invalid!");
-
-  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) return ConstantPointerNull::get(PointerType::get(Ty));
-  }
-
   return getGetElementPtrTy(PointerType::get(Ty), C, IdxList);
 }