[MS ABI] Add a mangling for _Complex

MSVC doesn't implement a mangling for C99's _Complex so we must invent
our own.

For now, treating it like a class type called _Complex in the __clang
namespace.

This means that 'void f(__Complex int))'
will demangle as: 'void f(struct __clang::_Complex<int>)'

llvm-svn: 256583

Author: majnemer

clang/lib/AST/MicrosoftMangle.cpp

@@ -2207,11 +2207,16 @@ void MicrosoftCXXNameMangler::mangleType(const RValueReferenceType *T,
 
 void MicrosoftCXXNameMangler::mangleType(const ComplexType *T, Qualifiers,
                                          SourceRange Range) {
-  DiagnosticsEngine &Diags = Context.getDiags();
-  unsigned DiagID = Diags.getCustomDiagID(DiagnosticsEngine::Error,
-    "cannot mangle this complex number type yet");
-  Diags.Report(Range.getBegin(), DiagID)
-    << Range;
+  QualType ElementType = T->getElementType();
+
+  llvm::SmallString<64> TemplateMangling;
+  llvm::raw_svector_ostream Stream(TemplateMangling);
+  MicrosoftCXXNameMangler Extra(Context, Stream);
+  Stream << "?$";
+  Extra.mangleSourceName("_Complex");
+  Extra.mangleType(ElementType, Range, QMM_Escape);
+
+  mangleArtificalTagType(TTK_Struct, TemplateMangling, {"__clang"});
 }
 
 void MicrosoftCXXNameMangler::mangleType(const VectorType *T, Qualifiers Quals,

clang/test/CodeGenCXX/mangle-ms.cpp

@@ -442,3 +442,7 @@ namespace Atomic {
 // CHECK-DAG: define void @"\01?f@Atomic@@YAXU?$_Atomic@H@__clang@@@Z"(
 void f(_Atomic(int)) {}
 }
+namespace Complex {
+// CHECK-DAG: define void @"\01?f@Complex@@YAXU?$_Complex@H@__clang@@@Z"(
+void f(_Complex int) {}
+}