[clang] nonblocking/nonallocating attributes (was: nolock/noalloc) (PR #84983)

[via cfe-commits]

================
@@ -0,0 +1,117 @@
+// RUN: %clang_cc1 %s -ast-dump -fblocks | FileCheck %s
+
+// Make sure that the attribute gets parsed and attached to the correct AST elements.
+
+#pragma clang diagnostic ignored "-Wunused-variable"
+
+// =========================================================================================
+// Square brackets, true
+
+namespace square_brackets {
+
+// On the type of the FunctionDecl
+void nl_function() [[clang::nonblocking]];
+// CHECK: FunctionDecl {{.*}} nl_function 'void () __attribute__((clang_nonblocking))'
+
+// On the type of the VarDecl holding a function pointer
+void (*nl_func_a)() [[clang::nonblocking]];
+// CHECK: VarDecl {{.*}} nl_func_a 'void (*)() __attribute__((clang_nonblocking))'
+
+// On the type of the ParmVarDecl of a function parameter
+static void nlReceiver(void (*nl_func)() [[clang::nonblocking]]);
+// CHECK: ParmVarDecl {{.*}} nl_func 'void (*)() __attribute__((clang_nonblocking))'
+
+// As an AttributedType within the nested types of a typedef
+typedef void (*nl_fp_type)() [[clang::nonblocking]];
+// CHECK: TypedefDecl {{.*}} nl_fp_type 'void (*)() __attribute__((clang_nonblocking))'
+using nl_fp_talias = void (*)() [[clang::nonblocking]];
+// CHECK: TypeAliasDecl {{.*}} nl_fp_talias 'void (*)() __attribute__((clang_nonblocking))'
+
+// From a typedef or typealias, on a VarDecl
+nl_fp_type nl_fp_var1;
+// CHECK: VarDecl {{.*}} nl_fp_var1 'nl_fp_type':'void (*)() __attribute__((clang_nonblocking))'
+nl_fp_talias nl_fp_var2;
+// CHECK: VarDecl {{.*}} nl_fp_var2 'nl_fp_talias':'void (*)() __attribute__((clang_nonblocking))'
+
+// On type of a FieldDecl
+struct Struct {
+	void (*nl_func_field)() [[clang::nonblocking]];
+// CHECK: FieldDecl {{.*}} nl_func_field 'void (*)() __attribute__((clang_nonblocking))'
+};
+
+// nonallocating should be subsumed into nonblocking
+void nl1() [[clang::nonblocking]] [[clang::nonallocating]];
+// CHECK: FunctionDecl {{.*}} nl1 'void () __attribute__((clang_nonblocking))'
----------------
Sirraide wrote:

This seems like a bad idea for source fidelity reasons; one *effect* subsuming the other in the function type sounds reasonable, but I think both *attributes* should still be present at the AST level.

https://github.com/llvm/llvm-project/pull/84983