Avoid passing nullptr to std::equal.

As documented in the LLVM Coding Standards, indeed MSVC incorrectly asserts 
on this in Debug mode. This happens when building clang with Visual C++ and
-triple i686-pc-windows-gnu on these clang regression tests:

 clang/test/CodeGen/2011-03-08-ZeroFieldUnionInitializer.c
 clang/test/CodeGen/empty-union-init.c

llvm-svn: 243996

1 files changed, 2 insertions, 1 deletions

diff --git a/llvm/lib/IR/Type.cpp b/llvm/lib/IR/Type.cpp
index 18c2e8c2b48..2f6dbab7201 100644
--- a/llvm/lib/IR/Type.cpp
+++ b/llvm/lib/IR/Type.cpp
@@ -612,7 +612,8 @@ bool StructType::isLayoutIdentical(StructType *Other) const {
       getNumElements() != Other->getNumElements())
     return false;
   
-  return std::equal(element_begin(), element_end(), Other->element_begin());
+  return element_begin() &&
+         std::equal(element_begin(), element_end(), Other->element_begin());
 }
 
 /// getTypeByName - Return the type with the specified name, or null if there