validation: add an internal decoration to allow atomic function parameters

Bug: tint: 927
Change-Id: Ia6f31bdbfa51c92b742faa89089649865bb45ad5
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/56020
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>

src/ast/disable_validation_decoration.cc

@@ -38,6 +38,8 @@ std::string DisableValidationDecoration::InternalName() const {
       return "disable_validation__ignore_storage_class";
     case DisabledValidation::kEntryPointParameter:
       return "disable_validation__entry_point_parameter";
+    case DisabledValidation::kIgnoreAtomicFunctionParameter:
+      return "disable_validation__ignore_atomic_function_parameter";
   }
   return "<invalid>";
 }

src/ast/disable_validation_decoration.h

@@ -37,6 +37,9 @@ enum class DisabledValidation {
   /// When applied to an entry-point function parameter, the validator will not
   /// check for entry IO decorations.
   kEntryPointParameter,
+  /// When applied to a function parameter, the validator will not
+  /// check if parameter type is atomic-free
+  kIgnoreAtomicFunctionParameter,
 };
 
 /// An internal decoration used to tell the validator to ignore specific