[DebugInfo] Add DIArgList MD to store multple values in DbgVariableIntrinsics

This patch adds a new metadata node, DIArgList, which contains a list of SSA
values. This node is in many ways similar in function to the existing
ValueAsMetadata node, with the difference being that it tracks a list instead of
a single value. Internally, it uses ValueAsMetadata to track the individual
values, but there is also a reasonable amount of DIArgList-specific
value-tracking logic on top of that. Similar to ValueAsMetadata, it is a special
case in parsing and printing due to the fact that it requires a function state
(as it may reference function-local values).

This patch should not result in any immediate functional change; it allows for
DIArgLists to be parsed and printed, but debug variable intrinsics do not yet
recognize them as a valid argument (outside of parsing).

Differential Revision: https://reviews.llvm.org/D88175

1 files changed, 10 insertions, 0 deletions

diff --git a/llvm/lib/Bitcode/Reader/MetadataLoader.cpp b/llvm/lib/Bitcode/Reader/MetadataLoader.cpp
index 8cdda62..0567f96 100644
--- a/llvm/lib/Bitcode/Reader/MetadataLoader.cpp
+++ b/llvm/lib/Bitcode/Reader/MetadataLoader.cpp
@@ -2076,6 +2076,16 @@ Error MetadataLoader::MetadataLoaderImpl::parseOneMetadata(
       return Err;
     break;
   }
+  case bitc::METADATA_ARG_LIST: {
+    SmallVector<ValueAsMetadata *, 4> Elts;
+    Elts.reserve(Record.size());
+    for (uint64_t Elt : Record)
+      Elts.push_back(dyn_cast_or_null<ValueAsMetadata>(getMDOrNull(Elt)));
+
+    MetadataList.assignValue(DIArgList::get(Context, Elts), NextMetadataNo);
+    NextMetadataNo++;
+    break;
+  }
   }
   return Error::success();
 #undef GET_OR_DISTINCT