SILGen: Emit enum element constructors using the 'on-demand' mechanism

Enum element constructors are used when an enum element satisfies
a protocol requirement. Instead of emitting them as part of
emitGlobalFunctionRef(), let's sink it down to getFunction() where
we do all other on-demand function body emission.

Author: slavapestov

lib/SILGen/SILGen.cpp

@@ -606,6 +606,8 @@ static bool isEmittedOnDemand(SILModule &M, SILDeclRef constant) {
 
     break;
   }
+  case SILDeclRef::Kind::EnumElement:
+    return true;
   default:
     break;
   }
@@ -828,7 +830,16 @@ static void emitDelayedFunction(SILGenModule &SGM,
     break;
   }
 
-  case SILDeclRef::Kind::EnumElement:
+  case SILDeclRef::Kind::EnumElement: {
+    auto *decl = cast<EnumElementDecl>(constant.getDecl());
+
+    SGM.preEmitFunction(constant, decl, f, decl);
+    PrettyStackTraceSILFunction X("silgen enum constructor", f);
+    SILGenFunction(SGM, *f, decl->getDeclContext()).emitEnumConstructor(decl);
+    SGM.postEmitFunction(constant, f);
+    break;
+  }
+
   case SILDeclRef::Kind::Destroyer:
   case SILDeclRef::Kind::Deallocator:
   case SILDeclRef::Kind::IVarInitializer:
@@ -1143,17 +1154,6 @@ void SILGenModule::emitConstructor(ConstructorDecl *decl) {
   }
 }
 
-void SILGenModule::emitEnumConstructor(EnumElementDecl *decl) {
-  // Enum element constructors are always emitted by need, so don't need
-  // delayed emission.
-  SILDeclRef constant(decl);
-  SILFunction *f = getFunction(constant, ForDefinition);
-  preEmitFunction(constant, decl, f, decl);
-  PrettyStackTraceSILFunction X("silgen enum constructor", f);
-  SILGenFunction(*this, *f, decl->getDeclContext()).emitEnumConstructor(decl);
-  postEmitFunction(constant, f);
-}
-
 SILFunction *SILGenModule::emitClosure(AbstractClosureExpr *ce) {
   SILDeclRef constant(ce);
   SILFunction *f = getFunction(constant, ForDefinition);

lib/SILGen/SILGen.h

@@ -284,10 +284,6 @@ class LLVM_LIBRARY_VISIBILITY SILGenModule : public ASTVisitor<SILGenModule> {
   /// SILDeclRef(cd, Destructor).
   void emitDestructor(ClassDecl *cd, DestructorDecl *dd);
 
-  /// Generates the enum constructor for the given
-  /// EnumElementDecl under the name SILDeclRef(decl).
-  void emitEnumConstructor(EnumElementDecl *decl);
-
   /// Emits the default argument generator with the given expression.
   void emitDefaultArgGenerator(SILDeclRef constant, ParamDecl *param);
 

lib/SILGen/SILGenThunk.cpp

@@ -138,8 +138,6 @@ SILGenFunction::emitGlobalFunctionRef(SILLocation loc, SILDeclRef constant,
       SGM.emitForeignToNativeThunk(constant);
     } else if (constant.isNativeToForeignThunk()) {
       SGM.emitNativeToForeignThunk(constant);
-    } else if (constant.kind == SILDeclRef::Kind::EnumElement) {
-      SGM.emitEnumConstructor(cast<EnumElementDecl>(constant.getDecl()));
     }
   }