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%.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@312144 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 13 insertions, 9 deletions

diff --git a/lib/Bitcode/Reader/MetadataLoader.cpp b/lib/Bitcode/Reader/MetadataLoader.cpp
index 10fbcdea784..3aadee457bf 100644
--- a/lib/Bitcode/Reader/MetadataLoader.cpp
+++ b/lib/Bitcode/Reader/MetadataLoader.cpp
@@ -497,8 +497,8 @@ class MetadataLoader::MetadataLoaderImpl {
           for (unsigned I = 0; I < GVs->getNumOperands(); I++)
             if (auto *GV =
                     dyn_cast_or_null<DIGlobalVariable>(GVs->getOperand(I))) {
-              auto *DGVE =
-                  DIGlobalVariableExpression::getDistinct(Context, GV, nullptr);
+              auto *DGVE = DIGlobalVariableExpression::getDistinct(
+                  Context, GV, DIExpression::get(Context, {}));
               GVs->replaceOperandWith(I, DGVE);
             }
       }
@@ -510,8 +510,8 @@ class MetadataLoader::MetadataLoaderImpl {
       GV.eraseMetadata(LLVMContext::MD_dbg);
       for (auto *MD : MDs)
         if (auto *DGV = dyn_cast_or_null<DIGlobalVariable>(MD)) {
-          auto *DGVE =
-              DIGlobalVariableExpression::getDistinct(Context, DGV, nullptr);
+          auto *DGVE = DIGlobalVariableExpression::getDistinct(
+              Context, DGV, DIExpression::get(Context, {}));
           GV.addMetadata(LLVMContext::MD_dbg, *DGVE);
         } else
           GV.addMetadata(LLVMContext::MD_dbg, *MD);
@@ -1585,7 +1585,8 @@ Error MetadataLoader::MetadataLoaderImpl::parseOneMetadata(
 
       DIGlobalVariableExpression *DGVE = nullptr;
       if (Attach || Expr)
-        DGVE = DIGlobalVariableExpression::getDistinct(Context, DGV, Expr);
+        DGVE = DIGlobalVariableExpression::getDistinct(
+            Context, DGV, Expr ? Expr : DIExpression::get(Context, {}));
       if (Attach)
         Attach->addDebugInfo(DGVE);
 
@@ -1648,10 +1649,13 @@ Error MetadataLoader::MetadataLoaderImpl::parseOneMetadata(
       return error("Invalid record");
 
     IsDistinct = Record[0];
-    MetadataList.assignValue(GET_OR_DISTINCT(DIGlobalVariableExpression,
-                                             (Context, getMDOrNull(Record[1]),
-                                              getMDOrNull(Record[2]))),
-                             NextMetadataNo);
+    Metadata *Expr = getMDOrNull(Record[2]);
+    if (!Expr)
+      Expr = DIExpression::get(Context, {});
+    MetadataList.assignValue(
+        GET_OR_DISTINCT(DIGlobalVariableExpression,
+                        (Context, getMDOrNull(Record[1]), Expr)),
+        NextMetadataNo);
     NextMetadataNo++;
     break;
   }