SwiftAsync: add Clang attribute to apply the LLVM `swiftasync` one.

Expected to be used by Swift runtime developers.

clang/include/clang/AST/Attr.h

@@ -208,6 +208,8 @@ public:
     switch (getKind()) {
     case attr::SwiftContext:
       return ParameterABI::SwiftContext;
+    case attr::SwiftAsyncContext:
+      return ParameterABI::SwiftAsyncContext;
     case attr::SwiftErrorResult:
       return ParameterABI::SwiftErrorResult;
     case attr::SwiftIndirectResult:

clang/include/clang/Basic/Attr.td

@@ -2457,6 +2457,11 @@ def SwiftContext : ParameterABIAttr {
   let Documentation = [SwiftContextDocs];
 }
 
+def SwiftAsyncContext : ParameterABIAttr {
+  let Spellings = [Clang<"swift_async_context">];
+  let Documentation = [SwiftAsyncContextDocs];
+}
+
 def SwiftErrorResult : ParameterABIAttr {
   let Spellings = [Clang<"swift_error_result">];
   let Documentation = [SwiftErrorResultDocs];

clang/include/clang/Basic/AttrDocs.td

@@ -4529,6 +4529,19 @@ A context parameter must have pointer or reference type.
   }];
 }
 
+def SwiftAsyncContextDocs : Documentation {
+  let Category = DocCatVariable;
+  let Content = [{
+The ``swift_async_context`` attribute marks a parameter as having the
+special asynchronous context-parameter ABI treatment.
+
+This treatment generally passes the context value in a special register
+which is normally callee-preserved.
+
+A context parameter must have pointer or reference type.
+  }];
+}
+
 def SwiftErrorResultDocs : Documentation {
   let Category = DocCatVariable;
   let Content = [{

clang/include/clang/Basic/Specifiers.h

@@ -344,7 +344,12 @@ namespace clang {
     /// This parameter (which must have pointer type) uses the special
     /// Swift context-pointer ABI treatment.  There can be at
     /// most one parameter on a given function that uses this treatment.
-    SwiftContext
+    SwiftContext,
+
+    /// This parameter (which must have pointer type) uses the special
+    /// Swift asynchronous context-pointer ABI treatment.  There can be at
+    /// most one parameter on a given function that uses this treatment.
+    SwiftAsyncContext,
   };
 
   /// Assigned inheritance model for a class in the MS C++ ABI. Must match order

clang/lib/AST/ItaniumMangle.cpp

@@ -3140,6 +3140,7 @@ CXXNameMangler::mangleExtParameterInfo(FunctionProtoType::ExtParameterInfo PI) {
 
   // All of these start with "swift", so they come before "ns_consumed".
   case ParameterABI::SwiftContext:
+  case ParameterABI::SwiftAsyncContext:
   case ParameterABI::SwiftErrorResult:
   case ParameterABI::SwiftIndirectResult:
     mangleVendorQualifier(getParameterABISpelling(PI.getABI()));

clang/lib/AST/TypePrinter.cpp

@@ -846,6 +846,8 @@ StringRef clang::getParameterABISpelling(ParameterABI ABI) {
     llvm_unreachable("asking for spelling of ordinary parameter ABI");
   case ParameterABI::SwiftContext:
     return "swift_context";
+  case ParameterABI::SwiftAsyncContext:
+    return "swift_async_context";
   case ParameterABI::SwiftErrorResult:
     return "swift_error_result";
   case ParameterABI::SwiftIndirectResult:

clang/lib/CodeGen/CGCall.cpp

@@ -2505,6 +2505,10 @@ void CodeGenModule::ConstructAttributeList(StringRef Name,
     case ParameterABI::SwiftContext:
       Attrs.addAttribute(llvm::Attribute::SwiftSelf);
       break;
+
+    case ParameterABI::SwiftAsyncContext:
+      Attrs.addAttribute(llvm::Attribute::SwiftAsync);
+      break;
     }
 
     if (FI.getExtParameterInfo(ArgNo).isNoEscape())

clang/lib/Sema/SemaDeclAttr.cpp

@@ -4896,6 +4896,14 @@ void Sema::AddParameterABIAttr(Decl *D, const AttributeCommonInfo &CI,
     D->addAttr(::new (Context) SwiftContextAttr(Context, CI));
     return;
 
+  case ParameterABI::SwiftAsyncContext:
+    if (!isValidSwiftContextType(type)) {
+      Diag(CI.getLoc(), diag::err_swift_abi_parameter_wrong_type)
+          << getParameterABISpelling(abi) << /*pointer to pointer */ 0 << type;
+    }
+    D->addAttr(::new (Context) SwiftAsyncContextAttr(Context, CI));
+    return;
+
   case ParameterABI::SwiftErrorResult:
     if (!isValidSwiftErrorResultType(type)) {
       Diag(CI.getLoc(), diag::err_swift_abi_parameter_wrong_type)
@@ -8104,6 +8112,9 @@ static void ProcessDeclAttribute(Sema &S, Scope *scope, Decl *D,
   case ParsedAttr::AT_SwiftContext:
     S.AddParameterABIAttr(D, AL, ParameterABI::SwiftContext);
     break;
+  case ParsedAttr::AT_SwiftAsyncContext:
+    S.AddParameterABIAttr(D, AL, ParameterABI::SwiftAsyncContext);
+    break;
   case ParsedAttr::AT_SwiftErrorResult:
     S.AddParameterABIAttr(D, AL, ParameterABI::SwiftErrorResult);
     break;

clang/lib/Sema/SemaType.cpp

@@ -2799,6 +2799,10 @@ static void checkExtParameterInfos(Sema &S, ArrayRef<QualType> paramTypes,
       checkForSwiftCC(paramIndex);
       continue;
 
+    case ParameterABI::SwiftAsyncContext:
+      // FIXME: might want to require swiftasynccc when it exists
+      continue;
+
     // swift_error parameters must be preceded by a swift_context parameter.
     case ParameterABI::SwiftErrorResult:
       checkForSwiftCC(paramIndex);

clang/test/CodeGen/arm-swiftcall.c

@@ -6,6 +6,7 @@
 #define OUT __attribute__((swift_indirect_result))
 #define ERROR __attribute__((swift_error_result))
 #define CONTEXT __attribute__((swift_context))
+#define ASYNC_CONTEXT __attribute__((swift_async_context))
 
 /*****************************************************************************/
 /****************************** PARAMETER ABIS *******************************/
@@ -53,6 +54,9 @@ void test_context_error_1() {
 SWIFTCALL void context_error_2(short s, CONTEXT int *self, ERROR float **error) {}
 // CHECK-LABEL: define{{.*}} void @context_error_2(i16{{.*}}, i32* swiftself{{.*}}, float** swifterror %0)
 
+SWIFTCALL void async_context_1(ASYNC_CONTEXT void *self) {}
+// CHECK-LABEL: define {{.*}} void @async_context_1(i8* swiftasync
+
 /*****************************************************************************/
 /********************************** LOWERING *********************************/
 /*****************************************************************************/

clang/test/Misc/pragma-attribute-supported-attributes-list.test

@@ -156,6 +156,7 @@
 // CHECK-NEXT: SpeculativeLoadHardening (SubjectMatchRule_function, SubjectMatchRule_objc_method)
 // CHECK-NEXT: StandaloneDebug (SubjectMatchRule_record)
 // CHECK-NEXT: SwiftAsync (SubjectMatchRule_function, SubjectMatchRule_objc_method)
+// CHECK-NEXT: SwiftAsyncContext (SubjectMatchRule_variable_is_parameter)
 // CHECK-NEXT: SwiftAsyncError (SubjectMatchRule_function, SubjectMatchRule_objc_method)
 // CHECK-NEXT: SwiftAsyncName (SubjectMatchRule_objc_method, SubjectMatchRule_function)
 // CHECK-NEXT: SwiftBridgedTypedef (SubjectMatchRule_type_alias)

clang/test/Sema/attr-swiftcall.c

@@ -5,6 +5,7 @@
 #define INDIRECT_RESULT __attribute__((swift_indirect_result))
 #define ERROR_RESULT __attribute__((swift_error_result))
 #define CONTEXT __attribute__((swift_context))
+#define ASYNC_CONTEXT __attribute__((swift_async_context))
 
 int notAFunction SWIFTCALL; // expected-warning {{'swiftcall' only applies to function types; type here is 'int'}}
 void variadic(int x, ...) SWIFTCALL; // expected-error {{variadic function cannot use swiftcall calling convention}}
@@ -29,3 +30,10 @@ void context_nonswift(CONTEXT void *context); // expected-error {{'swift_context
 void context_bad_type(CONTEXT int context) SWIFTCALL; // expected-error {{'swift_context' parameter must have pointer type; type here is 'int'}}
 void context_okay(CONTEXT void *context) SWIFTCALL;
 void context_okay2(CONTEXT void *context, void *selfType, char **selfWitnessTable) SWIFTCALL;
+
+void async_context_okay_for_now(ASYNC_CONTEXT void *context);
+void async_context_bad_type(ASYNC_CONTEXT int context) SWIFTCALL; // expected-error {{'swift_async_context' parameter must have pointer type; type here is 'int'}}
+void async_context_bad_pos(int context) ASYNC_CONTEXT SWIFTCALL; // expected-warning {{'swift_async_context' attribute only applies to parameters}}
+void async_context_bad_args(__attribute__((swift_async_context(1))) void *context) SWIFTCALL; // expected-error {{'swift_async_context' attribute takes no arguments}}
+void async_context_okay(ASYNC_CONTEXT void *context) SWIFTCALL;
+void async_context_okay2(ASYNC_CONTEXT void *context, void *selfType, char **selfWitnessTable) SWIFTCALL;