Staging flag for partial_apply simplification

include/swift/AST/Decl.h

@@ -3268,6 +3268,11 @@ class ClassDecl : public NominalTypeDecl {
   bool usesObjCGenericsModel() const {
     return isObjC() && hasClangNode() && isGenericContext();
   }
+
+  /// True if the class is known to be implemented in Swift.
+  bool hasKnownSwiftImplementation() const {
+    return !hasClangNode();
+  }
 };
 
 

include/swift/AST/SILOptions.h

@@ -108,6 +108,9 @@ class SILOptions {
   /// conventions.
   bool EnableGuaranteedClosureContexts = false;
 
+  /// Don't generate code using partial_apply in SIL generation.
+  bool DisableSILPartialApply = false;
+
   /// The name of the SIL outputfile if compiled with SIL debugging (-gsil).
   std::string SILOutputFileNameForDebugging;
 };

include/swift/Option/FrontendOptions.td

@@ -163,6 +163,9 @@ def disable_arc_opts : Flag<["-"], "disable-arc-opts">,
 def enable_guaranteed_closure_contexts : Flag<["-"], "enable-guaranteed-closure-contexts">,
   HelpText<"Use @guaranteed convention for closure context">;
 
+def disable_sil_partial_apply : Flag<["-"], "disable-sil-partial-apply">,
+  HelpText<"Disable use of partial_apply in SIL generation">;
+
 def remove_runtime_asserts : Flag<["-"], "remove-runtime-asserts">,
   HelpText<"Remove runtime asserts.">;
 

lib/Frontend/CompilerInvocation.cpp

@@ -1130,6 +1130,8 @@ static bool ParseSILArgs(SILOptions &Opts, ArgList &Args,
   Opts.EmitProfileCoverageMapping |= Args.hasArg(OPT_profile_coverage_mapping);
   Opts.EnableGuaranteedClosureContexts |=
     Args.hasArg(OPT_enable_guaranteed_closure_contexts);
+  Opts.DisableSILPartialApply |=
+    Args.hasArg(OPT_disable_sil_partial_apply);
 
   if (Args.hasArg(OPT_debug_on_sil)) {
     // Derive the name of the SIL file for debugging from

lib/IRGen/GenCast.cpp

@@ -151,7 +151,7 @@ llvm::Value *irgen::emitClassDowncast(IRGenFunction &IGF, llvm::Value *from,
 
   // If the destination type is known to have a Swift-compatible
   // implementation, use the most specific entrypoint.
-  if (destClass && hasKnownSwiftImplementation(IGF.IGM, destClass)) {
+  if (destClass && destClass->hasKnownSwiftImplementation()) {
     metadataRef = IGF.emitTypeMetadataRef(toType.getSwiftRValueType());
 
     switch (mode) {

lib/IRGen/GenClass.cpp

@@ -72,7 +72,7 @@ ReferenceCounting irgen::getReferenceCountingForClass(IRGenModule &IGM,
   // NOTE: if you change this, change Type::usesNativeReferenceCounting.
   // If the root class is implemented in swift, then we have a swift
   // refcount; otherwise, we have an ObjC refcount.
-  if (hasKnownSwiftImplementation(IGM, getRootClass(theClass)))
+  if (getRootClass(theClass)->hasKnownSwiftImplementation())
     return ReferenceCounting::Native;
 
   return ReferenceCounting::ObjC;
@@ -83,7 +83,7 @@ IsaEncoding irgen::getIsaEncodingForType(IRGenModule &IGM,
                                          CanType type) {
   if (auto theClass = type->getClassOrBoundGenericClass()) {
     // We can access the isas of pure Swift classes directly.
-    if (hasKnownSwiftImplementation(IGM, getRootClass(theClass)))
+    if (getRootClass(theClass)->hasKnownSwiftImplementation())
       return IsaEncoding::Pointer;
     // For ObjC or mixed classes, we need to use object_getClass.
     return IsaEncoding::ObjC;

lib/IRGen/GenMeta.cpp

@@ -435,12 +435,7 @@ bool irgen::hasKnownSwiftMetadata(IRGenModule &IGM, ClassDecl *theClass) {
   // is enough to conclusively force us into a slower path.
   // Eventually we might have an attribute here or something based on
   // the deployment target.
-  return hasKnownSwiftImplementation(IGM, theClass);
-}
-
-/// Is the given class known to have an implementation in Swift?
-bool irgen::hasKnownSwiftImplementation(IRGenModule &IGM, ClassDecl *theClass) {
-  return !theClass->hasClangNode();
+  return theClass->hasKnownSwiftImplementation();
 }
 
 /// Is the given method known to be callable by vtable lookup?
@@ -451,7 +446,7 @@ bool irgen::hasKnownVTableEntry(IRGenModule &IGM,
   if (!theClass) {
     return false;
   }
-  return hasKnownSwiftImplementation(IGM, theClass);
+  return theClass->hasKnownSwiftImplementation();
 }
 
 /// Is it basically trivial to access the given metadata?  If so, we don't

lib/IRGen/GenMeta.h

@@ -62,9 +62,6 @@ namespace irgen {
   /// metadata?
   bool hasKnownSwiftMetadata(IRGenModule &IGM, CanType theType);
 
-  /// Is the given class known to have an implementation in Swift?
-  bool hasKnownSwiftImplementation(IRGenModule &IGM, ClassDecl *theClass);
-
   /// Is the given method known to be callable by vtable dispatch?
   bool hasKnownVTableEntry(IRGenModule &IGM, AbstractFunctionDecl *theMethod);
 

lib/SIL/SILVerifier.cpp

@@ -996,6 +996,57 @@ class SILVerifier : public SILVerifierBase<SILVerifier> {
                 "function");
       }
     }
+
+    // TODO: Impose additional constraints when partial_apply when the
+    // -disable-sil-partial-apply flag is enabled. We want to reduce
+    // partial_apply to being only a means of associating a closure invocation
+    // function with its context.
+    //
+    // When we reach that point, we should be able to more deeply redesign
+    // PartialApplyInst to simplify the representation to carry a single
+    // argument.
+    if (PAI->getModule().getOptions().DisableSILPartialApply) {
+      // Should only be one context argument.
+      require(PAI->getArguments().size() == 1,
+              "partial_apply should have a single context argument");
+
+      // Callee should already have the thin convention, and result should be
+      // thick.
+      require(resultInfo->getRepresentation() ==
+                SILFunctionTypeRepresentation::Thick,
+              "partial_apply result should have thick convention");
+      require(PAI->getCallee()->getType().castTo<SILFunctionType>()
+                ->getRepresentation() ==
+              SILFunctionTypeRepresentation::Thin,
+              "partial_apply callee should have thin convention");
+
+      // TODO: Check that generic signature matches box's generic signature,
+      // once we have boxes with generic signatures.
+      require(!PAI->getCalleeFunction()->getGenericEnvironment(),
+              "partial_apply context must capture generic environment for "
+              "callee");
+
+      // Result's callee convention should match context argument's convention.
+      require(substTy->getParameters().back().getConvention()
+                == resultInfo->getCalleeConvention(),
+              "partial_apply context argument must have the same convention "
+              "as the resulting function's callee convention");
+
+      auto isSwiftRefcounted = [](SILType t) -> bool {
+        if (t.is<SILBoxType>())
+          return true;
+        if (t.getSwiftRValueType() == t.getASTContext().TheNativeObjectType)
+          return true;
+        if (auto clas = t.getClassOrBoundGenericClass())
+          // Must be a class defined in Swift.
+          return clas->hasKnownSwiftImplementation();
+        return false;
+      };
+
+      // The context argument must be a swift-refcounted box or class.
+      require(isSwiftRefcounted(PAI->getArguments().front()->getType()),
+              "partial_apply context argument must be swift-refcounted");
+    }
   }
 
   void checkBuiltinInst(BuiltinInst *BI) {

test/SIL/restricted-partial-apply.sil

@@ -0,0 +1,34 @@
+// RUN: %target-swift-frontend -module-name main -disable-sil-partial-apply -emit-sil -verify %s
+sil_stage canonical
+import Builtin
+
+class C {}
+
+sil @native_object_context : $@convention(thin) (@owned Builtin.NativeObject) -> ()
+sil @box_context : $@convention(thin) (@owned @box Builtin.Word) -> ()
+sil @class_context : $@convention(thin) (@owned C) -> ()
+
+sil @g_native_object_context : $@convention(thin) (@guaranteed Builtin.NativeObject) -> ()
+sil @g_box_context : $@convention(thin) (@guaranteed @box Builtin.Word) -> ()
+sil @g_class_context : $@convention(thin) (@guaranteed C) -> ()
+
+sil @limited_partial_applies : $@convention(thin) (Builtin.NativeObject, @box Builtin.Word, C) -> () {
+entry(%0 : $Builtin.NativeObject, %1 : $@box Builtin.Word, %2 : $C):
+  %a = function_ref @native_object_context : $@convention(thin) (@owned Builtin.NativeObject) -> ()
+  %b = function_ref @box_context : $@convention(thin) (@owned @box Builtin.Word) -> ()
+  %c = function_ref @class_context : $@convention(thin) (@owned C) -> ()
+
+  %d = function_ref @g_native_object_context : $@convention(thin) (@guaranteed Builtin.NativeObject) -> ()
+  %e = function_ref @g_box_context : $@convention(thin) (@guaranteed @box Builtin.Word) -> ()
+  %f = function_ref @g_class_context : $@convention(thin) (@guaranteed C) -> ()
+
+  %g = partial_apply %a(%0) : $@convention(thin) (@owned Builtin.NativeObject) -> ()
+  %h = partial_apply %b(%1) : $@convention(thin) (@owned @box Builtin.Word) -> ()
+  %i = partial_apply %c(%2) : $@convention(thin) (@owned C) -> ()
+
+  %j = partial_apply [callee_guaranteed] %d(%0) : $@convention(thin) (@guaranteed Builtin.NativeObject) -> ()
+  %k = partial_apply [callee_guaranteed] %e(%1) : $@convention(thin) (@guaranteed @box Builtin.Word) -> ()
+  %l = partial_apply [callee_guaranteed] %f(%2) : $@convention(thin) (@guaranteed C) -> ()
+
+  return undef : $()
+}