Merge pull request #16959 from huonw/tbd-thunk-specialization

[SIL]/[SILOpt] Thunks and specializations are never public.

Author: huonw

include/swift/SIL/SILFunction.h

@@ -40,7 +40,12 @@ class SILProfiler;
 enum IsBare_t { IsNotBare, IsBare };
 enum IsTransparent_t { IsNotTransparent, IsTransparent };
 enum Inline_t { InlineDefault, NoInline, AlwaysInline };
-enum IsThunk_t { IsNotThunk, IsThunk, IsReabstractionThunk };
+enum IsThunk_t {
+  IsNotThunk,
+  IsThunk,
+  IsReabstractionThunk,
+  IsSignatureOptimizedThunk
+};
 
 class SILSpecializeAttr final {
   friend SILFunction;
@@ -224,6 +229,33 @@ class SILFunction
   /// serialization.
   bool WasDeserializedCanonical = false;
 
+  static void
+  validateSubclassScope(SubclassScope scope, IsThunk_t isThunk,
+                        const GenericSpecializationInformation *genericInfo) {
+#ifndef NDEBUG
+    // The _original_ function for a method can turn into a thunk through
+    // signature optimization, meaning it needs to retain its subclassScope, but
+    // other thunks and specializations are implementation details and so
+    // shouldn't be connected to their parent class.
+    bool thunkCanHaveSubclassScope;
+    switch (isThunk) {
+    case IsNotThunk:
+    case IsSignatureOptimizedThunk:
+      thunkCanHaveSubclassScope = true;
+      break;
+    case IsThunk:
+    case IsReabstractionThunk:
+      thunkCanHaveSubclassScope = false;
+      break;
+    }
+    auto allowsInterestingScopes = thunkCanHaveSubclassScope && !genericInfo;
+    assert(
+        allowsInterestingScopes ||
+        scope == SubclassScope::NotApplicable &&
+            "SubclassScope on specialization or non-signature-optimized thunk");
+#endif
+  }
+
   SILFunction(SILModule &module, SILLinkage linkage, StringRef mangledName,
               CanSILFunctionType loweredType, GenericEnvironment *genericEnv,
               Optional<SILLocation> loc, IsBare_t isBareSILFunction,
@@ -573,13 +605,20 @@ class SILFunction
 
   /// Get this function's thunk attribute.
   IsThunk_t isThunk() const { return IsThunk_t(Thunk); }
-  void setThunk(IsThunk_t isThunk) { Thunk = isThunk; }
+  void setThunk(IsThunk_t isThunk) {
+    validateSubclassScope(getClassSubclassScope(), isThunk, SpecializationInfo);
+    Thunk = isThunk;
+  }
 
   /// Get the class visibility (relevant for class methods).
   SubclassScope getClassSubclassScope() const {
     return SubclassScope(ClassSubclassScope);
   }
-    
+  void setClassSubclassScope(SubclassScope scope) {
+    validateSubclassScope(scope, isThunk(), SpecializationInfo);
+    ClassSubclassScope = static_cast<unsigned>(scope);
+  }
+
   /// Get this function's noinline attribute.
   Inline_t getInlineStrategy() const { return Inline_t(InlineStrategy); }
   void setInlineStrategy(Inline_t inStr) { InlineStrategy = inStr; }
@@ -655,6 +694,7 @@ class SILFunction
 
   void setSpecializationInfo(const GenericSpecializationInformation *Info) {
     assert(!isSpecialization());
+    validateSubclassScope(getClassSubclassScope(), isThunk(), Info);
     SpecializationInfo = Info;
   }
 

lib/ParseSIL/ParseSIL.cpp

@@ -912,6 +912,8 @@ static bool parseDeclSILOptional(bool *isTransparent,
       *isCanonical = true;
     else if (isThunk && SP.P.Tok.getText() == "thunk")
       *isThunk = IsThunk;
+    else if (isThunk && SP.P.Tok.getText() == "signature_optimized_thunk")
+      *isThunk = IsSignatureOptimizedThunk;
     else if (isThunk && SP.P.Tok.getText() == "reabstraction_thunk")
       *isThunk = IsReabstractionThunk;
     else if (isGlobalInit && SP.P.Tok.getText() == "global_init")

lib/SIL/SILDeclRef.cpp

@@ -771,6 +771,10 @@ SubclassScope SILDeclRef::getSubclassScope() const {
   if (context->isExtensionContext())
     return SubclassScope::NotApplicable;
 
+  // Various forms of thunks don't either.
+  if (isThunk() || isForeign)
+    return SubclassScope::NotApplicable;
+
   auto *classType = context->getAsClassOrClassExtensionContext();
   if (!classType || classType->isFinal())
     return SubclassScope::NotApplicable;

lib/SIL/SILFunction.cpp

@@ -102,6 +102,8 @@ SILFunction::SILFunction(SILModule &Module, SILLinkage Linkage, StringRef Name,
       HasCReferences(false), IsWeakLinked(false),
       OptMode(OptimizationMode::NotSet), EffectsKindAttr(E),
       EntryCount(entryCount) {
+  validateSubclassScope(classSubclassScope, isThunk, nullptr);
+
   if (InsertBefore)
     Module.functions.insert(SILModule::iterator(InsertBefore), this);
   else

lib/SIL/SILPrinter.cpp

@@ -2326,6 +2326,9 @@ void SILFunction::print(SILPrintContext &PrintCtx) const {
   switch (isThunk()) {
   case IsNotThunk: break;
   case IsThunk: OS << "[thunk] "; break;
+  case IsSignatureOptimizedThunk:
+    OS << "[signature_optimized_thunk] ";
+    break;
   case IsReabstractionThunk: OS << "[reabstraction_thunk] "; break;
   }
 

lib/SILOptimizer/FunctionSignatureTransforms/FunctionSignatureOpts.cpp

@@ -506,6 +506,10 @@ void FunctionSignatureTransform::createFunctionSignatureOptimizedFunction() {
     NewF->setUnqualifiedOwnership();
   }
 
+  if (F->isSpecialization()) {
+    NewF->setSpecializationInfo(F->getSpecializationInfo());
+  }
+
   // Then we transfer the body of F to NewF.
   NewF->spliceBody(F);
 
@@ -529,7 +533,7 @@ void FunctionSignatureTransform::createFunctionSignatureOptimizedFunction() {
   }
 
   // Create the thunk body !
-  F->setThunk(IsThunk);
+  F->setThunk(IsSignatureOptimizedThunk);
   // The thunk now carries the information on how the signature is
   // optimized. If we inline the thunk, we will get the benefit of calling
   // the signature optimized function without additional setup on the

lib/SILOptimizer/IPO/ClosureSpecializer.cpp

@@ -635,11 +635,15 @@ ClosureSpecCloner::initCloned(const CallSiteDescriptor &CallSiteDesc,
       // and not the original linkage.
       // Otherwise the new function could have an external linkage (in case the
       // original function was de-serialized) and would not be code-gen'd.
+      // It's also important to disconnect this specialized function from any
+      // classes (the classSubclassScope), because that may incorrectly
+      // influence the linkage.
       getSpecializedLinkage(ClosureUser, ClosureUser->getLinkage()), ClonedName,
       ClonedTy, ClosureUser->getGenericEnvironment(),
       ClosureUser->getLocation(), IsBare, ClosureUser->isTransparent(),
       CallSiteDesc.isSerialized(), ClosureUser->getEntryCount(),
-      ClosureUser->isThunk(), ClosureUser->getClassSubclassScope(),
+      ClosureUser->isThunk(),
+      /*classSubclassScope=*/SubclassScope::NotApplicable,
       ClosureUser->getInlineStrategy(), ClosureUser->getEffectsKind(),
       ClosureUser, ClosureUser->getDebugScope());
   if (!ClosureUser->hasQualifiedOwnership()) {

lib/SILOptimizer/Utils/Generics.cpp

@@ -1840,6 +1840,7 @@ SILFunction *GenericFuncSpecializer::tryCreateSpecialization() {
   auto *Caller = ReInfo.getApply() ? ReInfo.getApply().getFunction() : nullptr;
   SubstitutionMap Subs = Caller ? ReInfo.getApply().getSubstitutionMap()
                                 : ReInfo.getClonerParamSubstitutionMap();
+  SpecializedF->setClassSubclassScope(SubclassScope::NotApplicable);
   SpecializedF->setSpecializationInfo(
       GenericSpecializationInformation::create(Caller, GenericFunc, Subs));
   return SpecializedF;

lib/Serialization/SILFormat.h

@@ -286,7 +286,7 @@ namespace sil_block {
       BCRecordLayout<SIL_FUNCTION, SILLinkageField,
                      BCFixed<1>,  // transparent
                      BCFixed<2>,  // serialized
-                     BCFixed<2>,  // thunk/reabstraction_thunk
+                     BCFixed<2>,  // thunks: signature optimized/reabstraction
                      BCFixed<1>,  // global_init
                      BCFixed<2>,  // inlineStrategy
                      BCFixed<2>,  // optimizationMode

test/SILOptimizer/dead_partial_apply_arg.swift

@@ -8,7 +8,7 @@ extension Int32 {
 
 // This function has an unused metatype argument.
 
-// CHECK-LABEL: sil [thunk] [always_inline] @$Ss5Int32V4testE8lessthan3lhs3rhsSbAB_ABtFZ : $@convention(method) (Int32, Int32, @thin Int32.Type) -> Bool
+// CHECK-LABEL: sil [signature_optimized_thunk] [always_inline] @$Ss5Int32V4testE8lessthan3lhs3rhsSbAB_ABtFZ : $@convention(method) (Int32, Int32, @thin Int32.Type) -> Bool
   public static func lessthan (lhs: Int32, rhs: Int32) -> Bool {
     return lhs < rhs
   }