SILGen: Introduce and adopt SILGenModule::shouldSkipDecl().

This method centralizes the logic for determining whether to skip emission of
SIL associated with a Decl.

Author: tshortli

include/swift/AST/DeclContext.h

@@ -877,15 +877,6 @@ class IterableDeclContext {
   /// The resulting list of members will be stable across translation units.
   ArrayRef<Decl *> getABIMembers() const;
 
-  using DeclsForLowering =
-      OptionalTransformRange<ArrayRef<Decl *>,
-                             AvailableDuringLoweringDeclFilter<Decl>>;
-
-  /// Get all of the members within this context that should be included when
-  /// lowering to SIL/IR, including any implicitly-synthesized members. The
-  /// decls returned by \c getABIMembers() are a superset of these decls.
-  DeclsForLowering getMembersForLowering() const;
-
   /// Get all of the members within this context, including any
   /// implicitly-synthesized members.
   ///

include/swift/SIL/SILVTableVisitor.h

@@ -105,6 +105,9 @@ template <class T> class SILVTableVisitor {
   }
 
   void maybeAddMember(Decl *member) {
+    if (!member->isAvailableDuringLowering())
+      return;
+
     if (isa<AccessorDecl>(member))
       /* handled as part of its storage */;
     else if (auto *fd = dyn_cast<FuncDecl>(member))
@@ -141,7 +144,7 @@ template <class T> class SILVTableVisitor {
     if (!theClass->hasKnownSwiftImplementation())
       return;
 
-    for (Decl *member : theClass->getMembersForLowering()) {
+    for (Decl *member : theClass->getABIMembers()) {
       maybeAddMember(member);
     }
   }

lib/AST/DeclContext.cpp

@@ -914,12 +914,6 @@ ArrayRef<Decl *> IterableDeclContext::getABIMembers() const {
       ArrayRef<Decl *>());
 }
 
-IterableDeclContext::DeclsForLowering
-IterableDeclContext::getMembersForLowering() const {
-  return DeclsForLowering(getABIMembers(),
-                          AvailableDuringLoweringDeclFilter<Decl>());
-}
-
 ArrayRef<Decl *> IterableDeclContext::getAllMembers() const {
   ASTContext &ctx = getASTContext();
   return evaluateOrDefault(

lib/SILGen/SILGen.cpp

@@ -797,8 +797,15 @@ bool SILGenModule::hasFunction(SILDeclRef constant) {
   return emittedFunctions.count(constant);
 }
 
-void SILGenModule::visit(Decl *D) {
+bool SILGenModule::shouldSkipDecl(Decl *D) {
   if (!D->isAvailableDuringLowering())
+    return true;
+
+  return false;
+}
+
+void SILGenModule::visit(Decl *D) {
+  if (shouldSkipDecl(D))
     return;
 
   ASTVisitor::visit(D);

lib/SILGen/SILGen.h

@@ -264,6 +264,9 @@ class LLVM_LIBRARY_VISIBILITY SILGenModule : public ASTVisitor<SILGenModule> {
   // Visitors for top-level forms
   //===--------------------------------------------------------------------===//
 
+  /// Returns true if SILGen should be skipped for the given decl.
+  bool shouldSkipDecl(Decl *d);
+
   void visit(Decl *D);
 
   // These are either not allowed at global scope or don't require

lib/SILGen/SILGenTopLevel.cpp

@@ -294,11 +294,18 @@ void SILGenTopLevel::visitTopLevelCodeDecl(TopLevelCodeDecl *TD) {
 SILGenTopLevel::TypeVisitor::TypeVisitor(SILGenFunction &SGF) : SGF(SGF) {}
 
 void SILGenTopLevel::TypeVisitor::emit(IterableDeclContext *Ctx) {
-  for (auto *Member : Ctx->getMembersForLowering()) {
+  for (auto *Member : Ctx->getABIMembers()) {
     visit(Member);
   }
 }
 
+void SILGenTopLevel::TypeVisitor::visit(Decl *D) {
+  if (SGF.SGM.shouldSkipDecl(D))
+    return;
+
+  TypeMemberVisitor::visit(D);
+}
+
 void SILGenTopLevel::TypeVisitor::visitPatternBindingDecl(
     PatternBindingDecl *PD) {
   for (auto i : range(PD->getNumPatternEntries())) {

lib/SILGen/SILGenTopLevel.h

@@ -49,6 +49,7 @@ class SILGenTopLevel : public ASTVisitor<SILGenTopLevel> {
     /// Emit `mark_function_escape` SIL instructions into `SGF` for encountered
     /// escape points.
     TypeVisitor(SILGenFunction &SGF);
+    void visit(Decl *D);
     void visitDecl(Decl *D) {}
     void emit(IterableDeclContext *Ctx);
     virtual void visitPatternBindingDecl(PatternBindingDecl *PD);

lib/SILGen/SILGenType.cpp

@@ -1098,7 +1098,7 @@ class SILGenType : public TypeMemberVisitor<SILGenType> {
   void emitType() {
     SGM.emitLazyConformancesForType(theType);
 
-    for (Decl *member : theType->getMembersForLowering()) {
+    for (Decl *member : theType->getABIMembers()) {
       visit(member);
     }
 
@@ -1141,6 +1141,13 @@ class SILGenType : public TypeMemberVisitor<SILGenType> {
   //===--------------------------------------------------------------------===//
   // Visitors for subdeclarations
   //===--------------------------------------------------------------------===//
+  void visit(Decl *D) {
+    if (SGM.shouldSkipDecl(D))
+      return;
+
+    TypeMemberVisitor::visit(D);
+  }
+
   void visitTypeAliasDecl(TypeAliasDecl *tad) {}
   void visitOpaqueTypeDecl(OpaqueTypeDecl *otd) {}
   void visitGenericTypeParamDecl(GenericTypeParamDecl *d) {}
@@ -1273,7 +1280,7 @@ class SILGenExtension : public TypeMemberVisitor<SILGenExtension> {
     // @_objcImplementation extension, but we don't actually need to do any of
     // the stuff that it currently does.
 
-    for (Decl *member : e->getMembersForLowering()) {
+    for (Decl *member : e->getABIMembers()) {
       visit(member);
     }
 
@@ -1300,6 +1307,13 @@ class SILGenExtension : public TypeMemberVisitor<SILGenExtension> {
   //===--------------------------------------------------------------------===//
   // Visitors for subdeclarations
   //===--------------------------------------------------------------------===//
+  void visit(Decl *D) {
+    if (SGM.shouldSkipDecl(D))
+      return;
+
+    TypeMemberVisitor::visit(D);
+  }
+
   void visitTypeAliasDecl(TypeAliasDecl *tad) {}
   void visitOpaqueTypeDecl(OpaqueTypeDecl *tad) {}
   void visitGenericTypeParamDecl(GenericTypeParamDecl *d) {}