SILGen: Drop value argument when lowering Builtin.sizeof/alignof/strideof.

The metatype value isn't needed to do the memory layout computation, and
IRGen only looks at the substitutions passed to the generic signature, so
we can reduce SIL code size, and avoid leaving behind useless metadata
accesses, if we don't emit it.

Author: jckarter

foo

@@ -557,12 +557,6 @@ BUILTIN_RUNTIME_CALL(IsOptionalType, "isOptional", "")
 /// Triggers a runtime failure if the condition is true.
 BUILTIN_MISC_OPERATION(CondFailMessage, "condfail_message", "", Special)
 
-/// Sizeof has type T.Type -> Int
-BUILTIN_MISC_OPERATION(Sizeof, "sizeof", "n", Special)
-
-/// Strideof has type T.Type -> Int
-BUILTIN_MISC_OPERATION(Strideof, "strideof", "n", Special)
-
 /// IsPOD has type T.Type -> Bool
 BUILTIN_MISC_OPERATION(IsPOD, "ispod", "n", Special)
 
@@ -580,9 +574,6 @@ BUILTIN_MISC_OPERATION(IsBitwiseTakable, "isbitwisetakable", "n", Special)
 /// IsSameMetatype has type (Any.Type, Any.Type) -> Bool
 BUILTIN_MISC_OPERATION(IsSameMetatype, "is_same_metatype", "n", Special)
 
-/// Alignof has type T.Type -> Int
-BUILTIN_MISC_OPERATION(Alignof, "alignof", "n", Special)
-
 /// AllocRaw has type (Int, Int) -> Builtin.RawPointer
 ///
 /// Parameters: object size, object alignment.
@@ -851,6 +842,15 @@ BUILTIN_MISC_OPERATION(AssumeAlignment, "assumeAlignment", "n", Special)
   BUILTIN_MISC_OPERATION(Id, Name, Attrs, Overload)
 #endif
 
+/// Sizeof has type T.Type -> Int
+BUILTIN_MISC_OPERATION_WITH_SILGEN(Sizeof, "sizeof", "n", Special)
+
+/// Strideof has type T.Type -> Int
+BUILTIN_MISC_OPERATION_WITH_SILGEN(Strideof, "strideof", "n", Special)
+
+/// Alignof has type T.Type -> Int
+BUILTIN_MISC_OPERATION_WITH_SILGEN(Alignof, "alignof", "n", Special)
+
 // getCurrentExecutor: () async -> Builtin.Executor?
 //
 // Retrieve the ExecutorRef on which the current asynchronous

include/swift/AST/Builtins.def

@@ -1419,6 +1419,43 @@ static ManagedValue emitBuiltinGetCurrentExecutor(
   return ManagedValue::forUnmanaged(SGF.emitGetCurrentExecutor(loc));
 }
 
+// Emit SIL for sizeof/strideof/alignof.
+// These formally take a metatype argument that's never actually used, so
+// we ignore it.
+static ManagedValue emitBuiltinSizeof(
+    SILGenFunction &SGF, SILLocation loc, SubstitutionMap subs,
+    PreparedArguments &&preparedArgs, SGFContext C) {
+  auto &ctx = SGF.getASTContext();
+  return ManagedValue::forUnmanaged(
+    SGF.B.createBuiltin(loc,
+      ctx.getIdentifier(getBuiltinName(BuiltinValueKind::Sizeof)),
+      SILType::getBuiltinWordType(ctx),
+      subs,
+      {}));
+}
+static ManagedValue emitBuiltinStrideof(
+    SILGenFunction &SGF, SILLocation loc, SubstitutionMap subs,
+    PreparedArguments &&preparedArgs, SGFContext C) {
+  auto &ctx = SGF.getASTContext();
+  return ManagedValue::forUnmanaged(
+    SGF.B.createBuiltin(loc,
+      ctx.getIdentifier(getBuiltinName(BuiltinValueKind::Strideof)),
+      SILType::getBuiltinWordType(ctx),
+      subs,
+      {}));
+}
+static ManagedValue emitBuiltinAlignof(
+    SILGenFunction &SGF, SILLocation loc, SubstitutionMap subs,
+    PreparedArguments &&preparedArgs, SGFContext C) {
+  auto &ctx = SGF.getASTContext();
+  return ManagedValue::forUnmanaged(
+    SGF.B.createBuiltin(loc,
+      ctx.getIdentifier(getBuiltinName(BuiltinValueKind::Alignof)),
+      SILType::getBuiltinWordType(ctx),
+      subs,
+      {}));
+}
+
 // Helper to lower a function argument to be usable as the entry point of a
 // new async task
 static ManagedValue

lib/SILGen/SILGenBuiltin.cpp

@@ -288,11 +288,13 @@ SILCombiner::optimizeAlignment(PointerToAddressInst *ptrAdrInst) {
                                     m_SILValue(extendedAlignment))))) {
     alignOper = extendedAlignment;
   }
-  MetatypeInst *metatype;
   if (match(alignOper,
-            m_ApplyInst(BuiltinValueKind::Alignof, m_MetatypeInst(metatype)))) {
+            m_ApplyInst(BuiltinValueKind::Alignof))) {
+    CanType formalType = cast<BuiltinInst>(alignOper)->getSubstitutions()
+      .getReplacementTypes()[0]->getCanonicalType(ptrAdrInst->getFunction()->getGenericSignature());
+
     SILType instanceType = ptrAdrInst->getFunction()->getLoweredType(
-        metatype->getType().castTo<MetatypeType>().getInstanceType());
+      Lowering::AbstractionPattern::getOpaque(), formalType);
 
     if (instanceType.getAddressType() != ptrAdrInst->getType())
       return nullptr;