[interop][SwiftToCxx] NFC, extract value witness extraction printing into shared printer

Author: hyp

lib/PrintAsClang/ClangSyntaxPrinter.cpp

@@ -127,3 +127,15 @@ void ClangSyntaxPrinter::printNullability(
   if (printKind != NullabilityPrintKind::After)
     os << ' ';
 }
+
+void ClangSyntaxPrinter::printSwiftTypeMetadataAccessFunctionCall(
+    StringRef name) {
+  os << name << "(0)";
+}
+
+void ClangSyntaxPrinter::printValueWitnessTableAccessFromTypeMetadata(
+    StringRef metadataVariable) {
+  os << "*(reinterpret_cast<";
+  printSwiftImplQualifier();
+  os << "ValueWitnessTable **>(" << metadataVariable << "._0) - 1)";
+}

lib/PrintAsClang/ClangSyntaxPrinter.h

@@ -77,6 +77,13 @@ class ClangSyntaxPrinter {
   static bool isClangKeyword(StringRef name);
   static bool isClangKeyword(Identifier name);
 
+  /// Print the call expression to the Swift type metadata access function.
+  void printSwiftTypeMetadataAccessFunctionCall(StringRef name);
+
+  /// Print the expression to access the value witness table pointer from the
+  /// given type metadata variable.
+  void printValueWitnessTableAccessFromTypeMetadata(StringRef metadataVariable);
+
 protected:
   raw_ostream &os;
 };

lib/PrintAsClang/PrintClangValueType.cpp

@@ -115,10 +115,12 @@ void ClangValueTypePrinter::printStructDecl(const StructDecl *SD) {
   printer.printBaseName(SD);
   os << "() {\n";
   os << "    auto metadata = " << cxx_synthesis::getCxxImplNamespaceName()
-     << "::" << typeMetadataFuncName << "(0);\n";
-  os << "    auto *vwTable = "
-        "*(reinterpret_cast<swift::_impl::ValueWitnessTable **>(metadata._0) - "
-        "1);\n";
+     << "::";
+  printer.printSwiftTypeMetadataAccessFunctionCall(typeMetadataFuncName);
+  os << ";\n";
+  os << "    auto *vwTable = ";
+  printer.printValueWitnessTableAccessFromTypeMetadata("metadata");
+  os << ";\n";
   os << "    vwTable->destroy(_getOpaquePointer(), metadata._0);\n";
   os << "  }\n";
 
@@ -128,10 +130,12 @@ void ClangValueTypePrinter::printStructDecl(const StructDecl *SD) {
   printer.printBaseName(SD);
   os << " &other) {\n";
   os << "    auto metadata = " << cxx_synthesis::getCxxImplNamespaceName()
-     << "::" << typeMetadataFuncName << "(0);\n";
-  os << "    auto *vwTable = "
-        "*(reinterpret_cast<swift::_impl::ValueWitnessTable **>(metadata._0) - "
-        "1);\n";
+     << "::";
+  printer.printSwiftTypeMetadataAccessFunctionCall(typeMetadataFuncName);
+  os << ";\n";
+  os << "    auto *vwTable = ";
+  printer.printValueWitnessTableAccessFromTypeMetadata("metadata");
+  os << ";\n";
   os << "    vwTable->initializeWithCopy(_getOpaquePointer(), const_cast<char "
         "*>(other._getOpaquePointer()), metadata._0);\n";
   os << "  }\n";