[DebugInfo] Add bitcode reader/writer for DILabel metadata.

[HsiangKai]

Summary

Create new MetadataCodes METADATA_LABEL. Bitcode reader will use GET_OR_DISTINCT()
to create DILabel objects and store the objects into LLVMContext.

In addition, implement bitcode writer in ModuleBitcodeWriter.

[chenwj]

I am not sure which fields of DILabel are required or optional, please double check yourself. I also feel bitcode patch can be combined with llvm assembly patch.

lib/Bitcode/Reader/MetadataLoader.cpp

1652

According D45025, should be Record.size() != 5?

[probinson]

It's usual to do bitcode and text reading/writing for new metadata all in one patch; splitting it up actually makes it harder to review.

[HsiangKai]

In D45026#1053411, @probinson wrote:

It's usual to do bitcode and text reading/writing for new metadata all in one patch; splitting it up actually makes it harder to review.

Merged into D45024. This patch should be abandoned.

include/llvm/Bitcode/LLVMBitCodes.h

enum MetadataCodes {
   METADATA_MODULE = 32,          // [distinct, scope, name, ...]
   METADATA_MACRO = 33,           // [distinct, macinfo, line, name, value]
   METADATA_MACRO_FILE = 34,      // [distinct, macinfo, line, file, ...]
   METADATA_STRINGS = 35,         // [count, offset] blob([lengths][chars])
   METADATA_GLOBAL_DECL_ATTACHMENT = 36, // [valueid, n x [id, mdnode]]
   METADATA_GLOBAL_VAR_EXPR = 37,        // [distinct, var, expr]
   METADATA_INDEX_OFFSET = 38,           // [offset]
   METADATA_INDEX = 39,                  // [bitpos]
+  METADATA_LABEL = 40,                  // [distinct, scope, name, file, line]
 };
 
 // The constants block (CONSTANTS_BLOCK_ID) describes emission for each
 // constant and maintains an implicit current type value.
 enum ConstantsCodes {
   CST_CODE_SETTYPE = 1,          // SETTYPE:       [typeid]
   CST_CODE_NULL = 2,             // NULL
   CST_CODE_UNDEF = 3,            // UNDEF

lib/Bitcode/Reader/MetadataLoader.cpp

case BitstreamEntry::Record: {
       case bitc::METADATA_LEXICAL_BLOCK_FILE:
       case bitc::METADATA_NAMESPACE:
       case bitc::METADATA_MACRO:
       case bitc::METADATA_MACRO_FILE:
       case bitc::METADATA_TEMPLATE_TYPE:
       case bitc::METADATA_TEMPLATE_VALUE:
       case bitc::METADATA_GLOBAL_VAR:
       case bitc::METADATA_LOCAL_VAR:
+      case bitc::METADATA_LABEL:
       case bitc::METADATA_EXPRESSION:
       case bitc::METADATA_OBJC_PROPERTY:
       case bitc::METADATA_IMPORTED_ENTITY:
       case bitc::METADATA_GLOBAL_VAR_EXPR:
         // We don't expect to see any of these, if we see one, give up on
         // lazy-loading and fallback.
         MDStringRef.clear();
         GlobalMetadataBitPosIndex.clear();
MetadataList.assignValue(
                          getMDString(Record[2 + HasTag]),
                          getMDOrNull(Record[3 + HasTag]), Record[4 + HasTag],
                          getDITypeRefOrNull(Record[5 + HasTag]),
                          Record[6 + HasTag], Flags, AlignInBits)),
         NextMetadataNo);
     NextMetadataNo++;
     break;
   }
+  case bitc::METADATA_LABEL: {
+    if (Record.size() < 4)
+      return error("Invalid record");
+
+    IsDistinct = Record[0] & 1;
+    MetadataList.assignValue(
+        GET_OR_DISTINCT(DILabel,
+                        (Context, getMDOrNull(Record[1]),
+                         getMDString(Record[2]),
+                         getMDOrNull(Record[3]), Record[4])),
+        NextMetadataNo);
+    NextMetadataNo++;
+    break;
+  }
   case bitc::METADATA_EXPRESSION: {
     if (Record.size() < 1)
       return error("Invalid record");
 
     IsDistinct = Record[0] & 1;
     uint64_t Version = Record[0] >> 1;
     auto Elts = MutableArrayRef<uint64_t>(Record).slice(1);
 

lib/Bitcode/Writer/BitcodeWriter.cpp

private:
   void writeDITemplateValueParameter(const DITemplateValueParameter *N,
                                      SmallVectorImpl<uint64_t> &Record,
                                      unsigned Abbrev);
   void writeDIGlobalVariable(const DIGlobalVariable *N,
                              SmallVectorImpl<uint64_t> &Record,
                              unsigned Abbrev);
   void writeDILocalVariable(const DILocalVariable *N,
                             SmallVectorImpl<uint64_t> &Record, unsigned Abbrev);
+  void writeDILabel(const DILabel *N,
+                    SmallVectorImpl<uint64_t> &Record, unsigned Abbrev);
   void writeDIExpression(const DIExpression *N,
                          SmallVectorImpl<uint64_t> &Record, unsigned Abbrev);
   void writeDIGlobalVariableExpression(const DIGlobalVariableExpression *N,
                                        SmallVectorImpl<uint64_t> &Record,
                                        unsigned Abbrev);
   void writeDIObjCProperty(const DIObjCProperty *N,
                            SmallVectorImpl<uint64_t> &Record, unsigned Abbrev);
   void writeDIImportedEntity(const DIImportedEntity *N,
void ModuleBitcodeWriter::writeDILocalVariable(
   Record.push_back(N->getArg());
   Record.push_back(N->getFlags());
   Record.push_back(N->getAlignInBits());
 
   Stream.EmitRecord(bitc::METADATA_LOCAL_VAR, Record, Abbrev);
   Record.clear();
 }
 
+void ModuleBitcodeWriter::writeDILabel(
+    const DILabel *N, SmallVectorImpl<uint64_t> &Record,
+    unsigned Abbrev) {
+  Record.push_back((uint64_t)N->isDistinct());
+  Record.push_back(VE.getMetadataOrNullID(N->getScope()));
+  Record.push_back(VE.getMetadataOrNullID(N->getRawName()));
+  Record.push_back(VE.getMetadataOrNullID(N->getFile()));
+  Record.push_back(N->getLine());
+
+  Stream.EmitRecord(bitc::METADATA_LABEL, Record, Abbrev);
+  Record.clear();
+}
+
 void ModuleBitcodeWriter::writeDIExpression(const DIExpression *N,
                                             SmallVectorImpl<uint64_t> &Record,
                                             unsigned Abbrev) {
   Record.reserve(N->getElements().size() + 1);
   const uint64_t Version = 3 << 1;
   Record.push_back((uint64_t)N->isDistinct() | Version);
   Record.append(N->elements_begin(), N->elements_end());