[IRGenSIL] Factor out shouldUseDispatchThunk() (NFC)

Author: adrian-prantl

lib/IRGen/IRGenSIL.cpp

@@ -1205,8 +1205,9 @@ class IRGenSILFunction :
   // SIL instruction lowering
   //===--------------------------------------------------------------------===//
 
-  void visitSILBasicBlock(SILBasicBlock *BB);
+  bool shouldUseDispatchThunk(SILDeclRef method);
 
+  void visitSILBasicBlock(SILBasicBlock *BB);
   void emitErrorResultVar(CanSILFunctionType FnTy,
                           SILResultInfo ErrorInfo,
                           DebugValueInst *DbgValue);
@@ -8414,17 +8415,7 @@ void IRGenSILFunction::visitObjCSuperMethodInst(swift::ObjCSuperMethodInst *i) {
                               /*startAtSuper=*/true);
 }
 
-void IRGenSILFunction::visitClassMethodInst(swift::ClassMethodInst *i) {
-  assert(!i->getMember().isForeign);
-
-  Explosion base = getLoweredExplosion(i->getOperand());
-  llvm::Value *baseValue = base.claimNext();
-
-  SILDeclRef method = i->getMember().getOverriddenVTableEntry();
-  PrettyStackTraceSILDeclRef entry("lowering class method call to", method);
-
-  auto methodType = i->getType().castTo<SILFunctionType>();
-
+bool IRGenSILFunction::shouldUseDispatchThunk(SILDeclRef method) {
   AccessLevel methodAccess = method.getDecl()->getEffectiveAccess();
   auto *classDecl = cast<ClassDecl>(method.getDecl()->getDeclContext());
   bool shouldUseDispatchThunk = false;
@@ -8452,9 +8443,22 @@ void IRGenSILFunction::visitClassMethodInst(swift::ClassMethodInst *i) {
     shouldUseDispatchThunk =
         classDecl->getModuleContext() != IGM.getSwiftModule();
   }
+  return shouldUseDispatchThunk;
+}
 
-  if (shouldUseDispatchThunk) {
-    llvm::Constant *fnPtr = IGM.getAddrOfDispatchThunk(method, NotForDefinition);
+void IRGenSILFunction::visitClassMethodInst(swift::ClassMethodInst *i) {
+  assert(!i->getMember().isForeign);
+
+  Explosion base = getLoweredExplosion(i->getOperand());
+  llvm::Value *baseValue = base.claimNext();
+
+  SILDeclRef method = i->getMember().getOverriddenVTableEntry();
+  PrettyStackTraceSILDeclRef entry("lowering class method call to", method);
+
+  auto methodType = i->getType().castTo<SILFunctionType>();
+  if (shouldUseDispatchThunk(method)) {
+    llvm::Constant *fnPtr =
+        IGM.getAddrOfDispatchThunk(method, NotForDefinition);
 
     if (methodType->isAsync()) {
       auto *fnPtrType = fnPtr->getType();