From: Dan Gohman <gohman@apple.com>
Date: Mon, 27 Jul 2009 21:59:50 +0000 (+0000)
Subject: Add a comment about the "getelementptr null" trick.
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=f08583b5323801b001175c2a62ac3e3d258723ac;p=oota-llvm.git

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
---

diff --git a/lib/VMCore/LLVMContext.cpp b/lib/VMCore/LLVMContext.cpp
index d7f4594e3ab..722e29ee5dc 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);