[Mangling] Allow standard substitutions in protocol mangling.

Protocol name mangling didn’t always go through a path that allowed the use
of standard substitutions. Enable standard substitutions for protocol name
manglings where they make sense.

Removes ~277k from the standard library binary size.

(cherry picked from commit f232af5)

Author: DougGregor

docs/ABI/Mangling.rst

@@ -329,8 +329,10 @@ Types
   any-generic-type ::= protocol 'P'              // nominal protocol type
   any-generic-type ::= context decl-name 'a'     // typealias type (used in DWARF and USRs)
 
-  any-generic-type ::= 'S' KNOWN-TYPE-KIND       // known nominal type substitution
-  any-generic-type ::= 'S' NATURAL KNOWN-TYPE-KIND    // repeated known type substitutions of the same kind
+  any-generic-type ::= standard-substitutions
+  
+  standard-substitutions ::= 'S' KNOWN-TYPE-KIND       // known nominal type substitution
+  standard-substitutions ::= 'S' NATURAL KNOWN-TYPE-KIND    // repeated known type substitutions of the same kind
 
   KNOWN-TYPE-KIND ::= 'A'                    // Swift.AutoreleasingUnsafeMutablePointer
   KNOWN-TYPE-KIND ::= 'a'                    // Swift.Array
@@ -383,6 +385,7 @@ Types
   KNOWN-TYPE-KIND ::= 'z'                    // Swift.BinaryInteger
 
   protocol ::= context decl-name
+  protocol ::= standard-substitutions
 
   type ::= 'Bb'                              // Builtin.BridgeObject
   type ::= 'BB'                              // Builtin.UnsafeValueBuffer

include/swift/AST/ASTMangler.h

@@ -208,7 +208,8 @@ class ASTMangler : public Mangler {
 
   void appendModule(const ModuleDecl *module);
 
-  void appendProtocolName(const ProtocolDecl *protocol);
+  void appendProtocolName(const ProtocolDecl *protocol,
+                          bool allowStandardSubstitution = true);
 
   void appendAnyGenericType(const GenericTypeDecl *decl);
 

lib/AST/ASTMangler.cpp

@@ -1492,7 +1492,11 @@ void ASTMangler::appendModule(const ModuleDecl *module) {
 }
 
 /// Mangle the name of a protocol as a substitution candidate.
-void ASTMangler::appendProtocolName(const ProtocolDecl *protocol) {
+void ASTMangler::appendProtocolName(const ProtocolDecl *protocol,
+                                    bool allowStandardSubstitution) {
+  if (allowStandardSubstitution && tryAppendStandardSubstitution(protocol))
+    return;
+
   appendContextOf(protocol);
   auto *clangDecl = protocol->getClangDecl();
   if (auto *clangProto = cast_or_null<clang::ObjCProtocolDecl>(clangDecl))

lib/Demangling/Demangler.cpp

@@ -1195,6 +1195,17 @@ NodePointer Demangler::popTypeList() {
 }
 
 NodePointer Demangler::popProtocol() {
+  if (NodePointer Type = popNode(Node::Kind::Type)) {
+    if (Type->getNumChildren() < 1)
+      return nullptr;
+
+    NodePointer Proto = Type->getChild(0);
+    if (Proto->getKind() != Node::Kind::Protocol)
+      return nullptr;
+
+    return Type;
+  }
+
   NodePointer Name = popNode(isDeclName);
   NodePointer Ctx = popContext();
   NodePointer Proto = createWithChildren(Node::Kind::Protocol, Ctx, Name);

lib/Demangling/OldRemangler.cpp

@@ -1754,6 +1754,9 @@ void Remangler::mangleProtocol(Node *node, EntityContext &ctx) {
 }
 
 void Remangler::mangleProtocolWithoutPrefix(Node *node) {
+  if (mangleStandardSubstitution(node))
+    return;
+
   if (node->getKind() == Node::Kind::Type) {
     assert(node->getNumChildren() == 1);
     node = node->begin()[0];

lib/Demangling/Remangler.cpp

@@ -248,6 +248,9 @@ class Remangler {
   }
 
   void manglePureProtocol(Node *Proto) {
+    if (mangleStandardSubstitution(Proto))
+      return;
+    
     Proto = skipType(Proto);
     mangleChildNodes(Proto);
   }
@@ -354,7 +357,8 @@ void Remangler::mangleIdentifierImpl(Node *node, bool isOperator) {
 
 bool Remangler::mangleStandardSubstitution(Node *node) {
   if (node->getKind() != Node::Kind::Structure
-      && node->getKind() != Node::Kind::Enum)
+      && node->getKind() != Node::Kind::Enum
+      && node->getKind() != Node::Kind::Protocol)
     return false;
 
   Node *context = node->getFirstChild();

lib/IRGen/IRGenMangler.cpp

@@ -120,7 +120,7 @@ std::string IRGenMangler::mangleTypeForLLVMTypeName(CanType Ty) {
   // don't start with a digit and don't need to be quoted.
   Buffer << 'T';
   if (auto P = dyn_cast<ProtocolType>(Ty)) {
-    appendProtocolName(P->getDecl());
+    appendProtocolName(P->getDecl(), /*allowStandardSubstitution=*/false);
     appendOperator("P");
   } else {
     appendType(Ty);

lib/IRGen/IRGenMangler.h

@@ -109,7 +109,7 @@ class IRGenMangler : public Mangle::ASTMangler {
 
   std::string mangleBareProtocol(const ProtocolDecl *Decl) {
     beginMangling();
-    appendProtocolName(Decl);
+    appendProtocolName(Decl, /*allowStandardSubstitution=*/false);
     appendOperator("P");
     return finalize();
   }
@@ -344,7 +344,7 @@ class IRGenMangler : public Mangle::ASTMangler {
 
   std::string mangleForProtocolDescriptor(ProtocolType *Proto) {
     beginMangling();
-    appendProtocolName(Proto->getDecl());
+    appendProtocolName(Proto->getDecl(), /*allowStandardSubstitution=*/false);
     appendOperator("P");
     return finalize();
   }

stdlib/public/SDK/Foundation/NSError.mm

@@ -21,7 +21,7 @@
   MANGLE_SYM(So10CFErrorRefas5Error10FoundationWa)();
 
 extern "C" const SWIFT_CC(swift) hashable_support::HashableWitnessTable *
-  MANGLE_SYM(So8NSObjectCs8Hashable10ObjectiveCWa)();
+  MANGLE_SYM(So8NSObjectCSH10ObjectiveCWa)();
 
 extern "C" SWIFT_CC(swift)
   NSDictionary *MANGLE_SYM(10Foundation24_getErrorDefaultUserInfoyyXlSgxs0C0RzlF)(
@@ -37,7 +37,7 @@
 // Define the bridging info struct.
 extern "C" ErrorBridgingInfo ERROR_BRIDGING_SYMBOL_NAME = {
   MANGLE_SYM(So10CFErrorRefas5Error10FoundationWa),
-  MANGLE_SYM(So8NSObjectCs8Hashable10ObjectiveCWa),
+  MANGLE_SYM(So8NSObjectCSH10ObjectiveCWa),
   MANGLE_SYM(10Foundation24_getErrorDefaultUserInfoyyXlSgxs0C0RzlF),
   MANGLE_SYM(10Foundation21_bridgeNSErrorToError_3outSbSo0C0C_SpyxGtAA021_ObjectiveCBridgeableE0RzlF),
   &MANGLE_SYM(10Foundation26_ObjectiveCBridgeableErrorMp)

stdlib/public/runtime/SwiftHashableSupport.h

@@ -19,8 +19,8 @@
 namespace swift {
 namespace hashable_support {
 
-extern "C" const ProtocolDescriptor PROTOCOL_DESCR_SYM(s8Hashable);
-static constexpr auto &HashableProtocolDescriptor = PROTOCOL_DESCR_SYM(s8Hashable);
+extern "C" const ProtocolDescriptor PROTOCOL_DESCR_SYM(SH);
+static constexpr auto &HashableProtocolDescriptor = PROTOCOL_DESCR_SYM(SH);
 
 struct HashableWitnessTable;