[SILGen] Fix swift_once initializer for lazy global var

`Builtin.once` has type `(Builtin.RawPointer, (Builtin.RawPointer) -> ())`
at Swift level, but lazy global init passes its initializer as `() -> ()`,
so their callee and caller signatures doesn't match.

Author: kateinoigakukun

include/swift/AST/Builtins.def

@@ -699,7 +699,7 @@ BUILTIN_MISC_OPERATION(IntToFPWithOverflow, "itofp_with_overflow", "n", Special)
 /// zeroInitializer has type <T> () -> T
 BUILTIN_MISC_OPERATION(ZeroInitializer, "zeroInitializer", "n", Special)
 
-/// once has type (Builtin.RawPointer, () -> ())
+/// once has type (Builtin.RawPointer, (Builtin.RawPointer) -> ())
 BUILTIN_MISC_OPERATION(Once, "once", "", Special)
 /// onceWithContext has type (Builtin.RawPointer, (Builtin.RawPointer) -> (), Builtin.RawPointer)
 BUILTIN_MISC_OPERATION(OnceWithContext, "onceWithContext", "", Special)

lib/SILGen/SILGen.cpp

@@ -1650,9 +1650,7 @@ SILFunction *SILGenModule::emitLazyGlobalInitializer(StringRef funcName,
   auto *onceBuiltin =
       cast<FuncDecl>(getBuiltinValueDecl(C, C.getIdentifier("once")));
   auto blockParam = onceBuiltin->getParameters()->get(1);
-  auto *type = blockParam->getType()->castTo<FunctionType>();
-  Type initType = FunctionType::get({}, TupleType::getEmpty(C),
-                                    type->getExtInfo());
+  auto *initType = blockParam->getType()->castTo<FunctionType>();
   auto initSILType = cast<SILFunctionType>(
       Types.getLoweredRValueType(TypeExpansionContext::minimal(), initType));
 

lib/SILGen/SILGenGlobalVariable.cpp

@@ -228,6 +228,12 @@ void SILGenFunction::emitLazyGlobalInitializer(PatternBindingDecl *binding,
                                                unsigned pbdEntry) {
   MagicFunctionName = SILGenModule::getMagicFunctionName(binding->getDeclContext());
 
+  // Add context pointer argument required to pass to `Builtin.once`
+  SILBasicBlock &entry = *F.begin();
+  SILType rawPointerSILTy
+    = getLoweredLoadableType(getASTContext().TheRawPointerType);
+  entry.createFunctionArgument(rawPointerSILTy);
+
   {
     Scope scope(Cleanups, binding);