[llvm][DebugInfo] Support versioned source language names in DwarfUnit (#162625)

Depends on:
* #162621

Now we can start emitting `DW_AT_language_name`, make sure
`DwarfUnit::getSourceLanguage` is equipped to handle this. Otherwise the
new test-case would assert.

Author: Michael137

llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp

@@ -704,9 +704,17 @@ void DwarfUnit::addType(DIE &Entity, const DIType *Ty,
   addDIEEntry(Entity, Attribute, DIEEntry(*getOrCreateTypeDIE(Ty)));
 }
 
+// FIXME: change callsites to use the new DW_LNAME_ language codes.
 llvm::dwarf::SourceLanguage DwarfUnit::getSourceLanguage() const {
-  return static_cast<llvm::dwarf::SourceLanguage>(
-      getLanguage().getUnversionedName());
+  const auto &Lang = getLanguage();
+
+  if (!Lang.hasVersionedName())
+    return static_cast<llvm::dwarf::SourceLanguage>(Lang.getName());
+
+  return llvm::dwarf::toDW_LANG(
+             static_cast<llvm::dwarf::SourceLanguageName>(Lang.getName()),
+             Lang.getVersion())
+      .value_or(llvm::dwarf::DW_LANG_hi_user);
 }
 
 std::string DwarfUnit::getParentContextString(const DIScope *Context) const {

llvm/test/DebugInfo/Generic/compileunit-source-language-name.ll

@@ -4,6 +4,11 @@
 
 @x = global i32 0, align 4, !dbg !0
 
+; Function Attrs: mustprogress noinline nounwind optnone ssp uwtable(sync)
+define void @_Z4funcv() !dbg !8 {
+  ret void, !dbg !11
+}
+
 !llvm.dbg.cu = !{!2}
 !llvm.module.flags = !{!6, !7}
 
@@ -15,3 +20,7 @@
 !5 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
 !6 = !{i32 7, !"Dwarf Version", i32 5}
 !7 = !{i32 2, !"Debug Info Version", i32 3}
+!8 = distinct !DISubprogram(name: "func", linkageName: "_Z4funcv", scope: !3, file: !3, line: 2, type: !9, scopeLine: 2, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !2)
+!9 = !DISubroutineType(types: !10)
+!10 = !{null}
+!11 = !DILocation(line: 2, column: 14, scope: !8)