[Assignment Tracking][3/*] Add DIAssignID metadata boilerplate

The Assignment Tracking debug-info feature is outlined in this RFC:

https://discourse.llvm.org/t/
rfc-assignment-tracking-a-better-way-of-specifying-variable-locations-in-ir

Add the DIAssignID metadata attachment boilerplate. Includes a textual-bitcode
roundtrip test and tests that the verifier and parser catch badly formed IR.

This piece of metadata links together stores (used as an attachment) and the
yet-to-be-added llvm.dbg.assign debug intrinsic (used as an operand).

Reviewed By: jmorse

Differential Revision: https://reviews.llvm.org/D132222

1 files changed, 13 insertions, 0 deletions

diff --git a/llvm/lib/Bitcode/Reader/MetadataLoader.cpp b/llvm/lib/Bitcode/Reader/MetadataLoader.cpp
index 02d76f6..1ac1502 100644
--- a/llvm/lib/Bitcode/Reader/MetadataLoader.cpp
+++ b/llvm/lib/Bitcode/Reader/MetadataLoader.cpp
@@ -856,6 +856,7 @@ MetadataLoader::MetadataLoaderImpl::lazyLoadModuleMetadataBlock() {
       case bitc::METADATA_TEMPLATE_VALUE:
       case bitc::METADATA_GLOBAL_VAR:
       case bitc::METADATA_LOCAL_VAR:
+      case bitc::METADATA_ASSIGN_ID:
       case bitc::METADATA_LABEL:
       case bitc::METADATA_EXPRESSION:
       case bitc::METADATA_OBJC_PROPERTY:
@@ -1964,6 +1965,18 @@ Error MetadataLoader::MetadataLoaderImpl::parseOneMetadata(
 
     break;
   }
+  case bitc::METADATA_ASSIGN_ID: {
+    if (Record.size() != 1)
+      return error("Invalid DIAssignID record.");
+
+    IsDistinct = Record[0] & 1;
+    if (!IsDistinct)
+      return error("Invalid DIAssignID record. Must be distinct");
+
+    MetadataList.assignValue(DIAssignID::getDistinct(Context), NextMetadataNo);
+    NextMetadataNo++;
+    break;
+  }
   case bitc::METADATA_LOCAL_VAR: {
     // 10th field is for the obseleted 'inlinedAt:' field.
     if (Record.size() < 8 || Record.size() > 10)