Add a generalized form of ConstantExpr::getOffsetOf which works for

array types as well as struct types, and which accepts arbitrary
Constant indicies.  

llvm-svn: 94981

2 files changed, 17 insertions, 7 deletions

diff --git a/llvm/include/llvm/Constants.h b/llvm/include/llvm/Constants.h
index 58077f0eb23..4111f36c5f0 100644
--- a/llvm/include/llvm/Constants.h
+++ b/llvm/include/llvm/Constants.h
@@ -652,10 +652,15 @@ public:
   ///
   static Constant *getSizeOf(const Type* Ty);
 
-  /// getOffsetOf constant expr - computes the offset of a field in a target
-  /// independent way (Note: the return type is an i64).
+  /// getOffsetOf constant expr - computes the offset of a struct field in a 
+  /// target independent way (Note: the return type is an i64).
+  ///
+  static Constant *getOffsetOf(const StructType* STy, unsigned FieldNo);
+
+  /// getOffsetOf constant expr - This is a generalized form of getOffsetOf,
+  /// which supports any aggregate type, and any Constant index.
   ///
-  static Constant *getOffsetOf(const StructType* Ty, unsigned FieldNo);
+  static Constant *getOffsetOf(const Type* Ty, Constant *FieldNo);
   
   static Constant *getNeg(Constant *C);
   static Constant *getFNeg(Constant *C);
diff --git a/llvm/lib/VMCore/Constants.cpp b/llvm/lib/VMCore/Constants.cpp
index 1415944885b..b1c942c214f 100644
--- a/llvm/lib/VMCore/Constants.cpp
+++ b/llvm/lib/VMCore/Constants.cpp
@@ -1493,16 +1493,21 @@ Constant* ConstantExpr::getAlignOf(const Type* Ty) {
 }
 
 Constant* ConstantExpr::getOffsetOf(const StructType* STy, unsigned FieldNo) {
+  return getOffsetOf(STy, ConstantInt::get(Type::getInt32Ty(STy->getContext()),
+                                           FieldNo));
+}
+
+Constant* ConstantExpr::getOffsetOf(const Type* Ty, Constant *FieldNo) {
   // offsetof is implemented as: (i64) gep (Ty*)null, 0, FieldNo
   // Note that a non-inbounds gep is used, as null isn't within any object.
   Constant *GEPIdx[] = {
-    ConstantInt::get(Type::getInt64Ty(STy->getContext()), 0),
-    ConstantInt::get(Type::getInt32Ty(STy->getContext()), FieldNo)
+    ConstantInt::get(Type::getInt64Ty(Ty->getContext()), 0),
+    FieldNo
   };
   Constant *GEP = getGetElementPtr(
-                Constant::getNullValue(PointerType::getUnqual(STy)), GEPIdx, 2);
+                Constant::getNullValue(PointerType::getUnqual(Ty)), GEPIdx, 2);
   return getCast(Instruction::PtrToInt, GEP,
-                 Type::getInt64Ty(STy->getContext()));
+                 Type::getInt64Ty(Ty->getContext()));
 }
 
 Constant *ConstantExpr::getCompare(unsigned short pred,