Don't use -1 as a value of an unsigned 7-bit enumeration; that has undefined

behavior and violates the !range constraints we put on loads of this enum.
Found by clang -fsanitize=enum.

llvm-svn: 170653

llvm/include/llvm/DataLayout.h

@@ -39,6 +39,7 @@ class ArrayRef;
 
 /// Enum used to categorize the alignment types stored by LayoutAlignElem
 enum AlignTypeEnum {
+  INVALID_ALIGN = 0,                 ///< An invalid alignment
   INTEGER_ALIGN = 'i',               ///< Integer type alignment
   VECTOR_ALIGN = 'v',                ///< Vector type alignment
   FLOAT_ALIGN = 'f',                 ///< Floating point type alignment

llvm/lib/VMCore/DataLayout.cpp

@@ -118,8 +118,7 @@ LayoutAlignElem::operator==(const LayoutAlignElem &rhs) const {
 }
 
 const LayoutAlignElem
-DataLayout::InvalidAlignmentElem =
-            LayoutAlignElem::get((AlignTypeEnum) -1, 0, 0, 0);
+DataLayout::InvalidAlignmentElem = LayoutAlignElem::get(INVALID_ALIGN, 0, 0, 0);
 
 //===----------------------------------------------------------------------===//
 // PointerAlignElem, PointerAlign support