Canonicalize the representation of empty an expression in DIGlobalVariableExpression

This change simplifies code that has to deal with
DIGlobalVariableExpression and mirrors how we treat DIExpressions in
debug info intrinsics. Before this change there were two ways of
representing empty expressions on globals, a nullptr and an empty
!DIExpression().

If someone needs to upgrade out-of-tree testcases:
  perl -pi -e 's/(!DIGlobalVariableExpression\(var: ![0-9]*)\)/\1, expr: !DIExpression())/g' <MYTEST.ll>
will catch 95%.

llvm-svn: 312144

1 files changed, 2 insertions, 0 deletions

diff --git a/llvm/lib/IR/DIBuilder.cpp b/llvm/lib/IR/DIBuilder.cpp
index 5d4181a2c51..1bd9d557b8f 100644
--- a/llvm/lib/IR/DIBuilder.cpp
+++ b/llvm/lib/IR/DIBuilder.cpp
@@ -595,6 +595,8 @@ DIGlobalVariableExpression *DIBuilder::createGlobalVariableExpression(
       VMContext, cast_or_null<DIScope>(Context), Name, LinkageName, F,
       LineNumber, Ty, isLocalToUnit, true, cast_or_null<DIDerivedType>(Decl),
       AlignInBits);
+  if (!Expr)
+    Expr = createExpression();
   auto *N = DIGlobalVariableExpression::get(VMContext, GV, Expr);
   AllGVs.push_back(N);
   return N;