demangler: also support the future mangling prefix ‘_S’

Author: eeckstein

lib/Basic/Demangle.cpp

@@ -2331,7 +2331,9 @@ class OldDemangler {
 bool
 swift::Demangle::isSwiftSymbol(const char *mangledName) {
   // The old mangling.
-  if (mangledName[0] == '_' && mangledName[1] == 'T')
+  if (mangledName[0] == '_'
+      // Also accept the future mangling prefix.
+      && (mangledName[1] == 'T' || mangledName[1] == 'S'))
     return true;
 
   // The new mangling.

lib/Basic/Demangler.cpp

@@ -137,7 +137,10 @@ void Context::clear() {
 
 NodePointer Context::demangleSymbolAsNode(llvm::StringRef MangledName) {
 #ifndef NO_NEW_DEMANGLING
-  if (MangledName.startswith(MANGLING_PREFIX_STR)) {
+  if (MangledName.startswith(MANGLING_PREFIX_STR)
+      // Also accept the future mangling prefix.
+      // TODO: remove this line as soon as MANGLING_PREFIX_STR gets "_S".
+      || MangledName.startswith("_S")) {
     return D->demangleSymbol(MangledName);
   }
 #endif
@@ -171,7 +174,10 @@ std::string Context::demangleTypeAsString(llvm::StringRef MangledName,
 }
 
 bool Context::isThunkSymbol(llvm::StringRef MangledName) {
-  if (MangledName.startswith(MANGLING_PREFIX_STR)) {
+  if (MangledName.startswith(MANGLING_PREFIX_STR)
+      // Also accept the future mangling prefix.
+      // TODO: remove this line as soon as MANGLING_PREFIX_STR gets "_S".
+      || MangledName.startswith("_S")) {
     // First do a quick check
     if (MangledName.endswith("TA") ||  // partial application forwarder
         MangledName.endswith("Ta") ||  // ObjC partial application forwarder
@@ -341,7 +347,10 @@ void Demangler::init(StringRef MangledName) {
 NodePointer Demangler::demangleSymbol(StringRef MangledName) {
   init(MangledName);
 
-  if (!nextIf(MANGLING_PREFIX_STR))
+  if (!nextIf(MANGLING_PREFIX_STR)
+      // Also accept the future mangling prefix.
+      // TODO: remove this line as soon as MANGLING_PREFIX_STR gets "_S".
+      && !nextIf("_S"))
     return nullptr;
 
   NodePointer topLevel = createNode(Node::Kind::Global);

test/Demangle/Inputs/manglings.txt

@@ -81,6 +81,8 @@ _TToFC3foo3bar3basfT3zimCS_3zim_T_ ---> {TC} @objc foo.bar.bas (zim : foo.zim) -
 _TTOFSC3fooFTSdSd_Sd ---> {T} @nonobjc __C.foo (Swift.Double, Swift.Double) -> Swift.Double
 _T03foo3barC3basyAA3zimCAE_tFTo ---> {TC} @objc foo.bar.bas (zim : foo.zim) -> ()
 _T0SC3fooSdSd_SdtFTO ---> {T} @nonobjc __C.foo (Swift.Double, Swift.Double) -> Swift.Double
+_S3foo3barC3basyAA3zimCAE_tFTo ---> {TC} @objc foo.bar.bas (zim : foo.zim) -> ()
+_SSC3fooSdSd_SdtFTO ---> {T} @nonobjc __C.foo (Swift.Double, Swift.Double) -> Swift.Double
 _TTDFC3foo3bar3basfT3zimCS_3zim_T_ ---> dynamic foo.bar.bas (zim : foo.zim) -> ()
 _TFC3foo3bar3basfT3zimCS_3zim_T_ ---> foo.bar.bas (zim : foo.zim) -> ()
 _TF3foooi1pFTCS_3barVS_3bas_OS_3zim ---> foo.+ infix (foo.bar, foo.bas) -> foo.zim

tools/swift-demangle/swift-demangle.cpp

@@ -99,8 +99,15 @@ static void demangle(llvm::raw_ostream &os, llvm::StringRef name,
       // mangling and demangling tests.
       remangled = name;
     } else {
+      // Also accept the future mangling prefix.
+      // TODO: remove the "_S" as soon as MANGLING_PREFIX_STR gets "_S".
       remangled = swift::Demangle::mangleNode(pointer,
-                          /*NewMangling*/ name.startswith(MANGLING_PREFIX_STR));
+                          /*NewMangling*/ name.startswith(MANGLING_PREFIX_STR)
+                                          || name.startswith("_S"));
+      if (name.startswith("_S")) {
+        assert(remangled.find(MANGLING_PREFIX_STR) == 0);
+        remangled = "_S" + remangled.substr(3);
+      }
       if (name != remangled) {
         llvm::errs() << "\nError: re-mangled name \n  " << remangled
                      << "\ndoes not match original name\n  " << name << '\n';
@@ -144,7 +151,9 @@ static void demangle(llvm::raw_ostream &os, llvm::StringRef name,
 
 static int demangleSTDIN(const swift::Demangle::DemangleOptions &options) {
   // This doesn't handle Unicode symbols, but maybe that's okay.
-  llvm::Regex maybeSymbol("(_T|" MANGLING_PREFIX_STR ")[_a-zA-Z0-9$]+");
+  // Also accept the future mangling prefix.
+  // TODO: remove the "_S" as soon as MANGLING_PREFIX_STR gets "_S".
+  llvm::Regex maybeSymbol("(_T|_S|" MANGLING_PREFIX_STR ")[_a-zA-Z0-9$]+");
 
   swift::Demangle::Context DCtx;
   for (std::string mangled; std::getline(std::cin, mangled);) {