From f08583b5323801b001175c2a62ac3e3d258723ac Mon Sep 17 00:00:00 2001
From: Dan Gohman <gohman@apple.com>
Date: Mon, 27 Jul 2009 21:59:50 +0000
Subject: Add a comment about the "getelementptr null" trick.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@77262 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/VMCore/LLVMContext.cpp | 1 +
 1 file changed, 1 insertion(+)

(limited to 'lib/VMCore')

diff --git a/lib/VMCore/LLVMContext.cpp b/lib/VMCore/LLVMContext.cpp
index d7f4594..722e29e 100644
--- a/lib/VMCore/LLVMContext.cpp
+++ b/lib/VMCore/LLVMContext.cpp
@@ -419,6 +419,7 @@ Constant* LLVMContext::getConstantExprInsertValue(Constant* Agg, Constant* Val,
 
 Constant* LLVMContext::getConstantExprSizeOf(const Type* Ty) {
   // sizeof is implemented as: (i64) gep (Ty*)null, 1
+  // Note that a non-inbounds gep is used, as null isn't within any object.
   Constant *GEPIdx = ConstantInt::get(Type::Int32Ty, 1);
   Constant *GEP = getConstantExprGetElementPtr(
                             getNullValue(getPointerTypeUnqual(Ty)), &GEPIdx, 1);
-- 
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