From a893aad8fbfb24e98097c1bc3b1fdccae217a6c0 Mon Sep 17 00:00:00 2001
From: Alkis Evlogimenos <alkis@evlogimenos.com>
Date: Sun, 24 Oct 2004 01:41:10 +0000
Subject: [PATCH] Add ConstantExpr::getSizeOf(Type*).

llvm-svn: 17196
---
 include/llvm/Constants.h | 4 ++++
 lib/VMCore/Constants.cpp | 9 +++++++++
 2 files changed, 13 insertions(+)

diff --git a/include/llvm/Constants.h b/include/llvm/Constants.h
index 6a59cfa732b..502974dc779 100644
--- a/include/llvm/Constants.h
+++ b/include/llvm/Constants.h
@@ -557,6 +557,10 @@ public:
     return getSelectTy(V1->getType(), C, V1, V2);
   }
 
+  /// getSizeOf constant expr - computes the size of a type in a
+  /// target independent way
+  ///
+  static Constant *getSizeOf(const Type *Ty);
 
   /// ConstantExpr::get - Return a binary or shift operator constant expression,
   /// folding if possible.
diff --git a/lib/VMCore/Constants.cpp b/lib/VMCore/Constants.cpp
index 77aa23135e5..3d2e658e634 100644
--- a/lib/VMCore/Constants.cpp
+++ b/lib/VMCore/Constants.cpp
@@ -1244,6 +1244,15 @@ Constant *ConstantExpr::getZeroExtend(Constant *C, const Type *Ty) {
   return ConstantExpr::getCast(C, Ty);
 }
 
+Constant *ConstantExpr::getSizeOf(const Type *Ty) {
+  // sizeof is implemented as: (unsigned) gep (Ty)null, 1
+  return getCast(
+    getGetElementPtr(
+      getNullValue(Ty),
+      std::vector<Constant*>(1, ConstantInt::get(Type::UByteTy, 1))),
+    Type::UIntTy);
+}
+
 Constant *ConstantExpr::getTy(const Type *ReqTy, unsigned Opcode,
                               Constant *C1, Constant *C2) {
   if (Opcode == Instruction::Shl || Opcode == Instruction::Shr)