convert the optimize attribute to a new parser

compiler/rustc_attr_parsing/src/attributes/codegen_attrs.rs

@@ -0,0 +1,40 @@
+use rustc_attr_data_structures::{AttributeKind, OptimizeAttr};
+use rustc_feature::{AttributeTemplate, template};
+use rustc_span::sym;
+
+use super::{AttributeOrder, OnDuplicate, SingleAttributeParser};
+use crate::context::{AcceptContext, Stage};
+use crate::parser::ArgParser;
+
+pub(crate) struct OptimizeParser;
+
+impl<S: Stage> SingleAttributeParser<S> for OptimizeParser {
+    const PATH: &[rustc_span::Symbol] = &[sym::optimize];
+    const ATTRIBUTE_ORDER: AttributeOrder = AttributeOrder::KeepLast;
+    const ON_DUPLICATE: OnDuplicate<S> = OnDuplicate::WarnButFutureError;
+    const TEMPLATE: AttributeTemplate = template!(List: "size|speed|none");
+
+    fn convert(cx: &mut AcceptContext<'_, '_, S>, args: &ArgParser<'_>) -> Option<AttributeKind> {
+        let Some(list) = args.list() else {
+            cx.expected_list(cx.attr_span);
+            return None;
+        };
+
+        let Some(single) = list.single() else {
+            cx.expected_single_argument(list.span);
+            return None;
+        };
+
+        let res = match single.meta_item().and_then(|i| i.path().word().map(|i| i.name)) {
+            Some(sym::size) => OptimizeAttr::Size,
+            Some(sym::speed) => OptimizeAttr::Speed,
+            Some(sym::none) => OptimizeAttr::DoNotOptimize,
+            _ => {
+                cx.expected_specific_argument(single.span(), vec!["size", "speed", "none"]);
+                OptimizeAttr::Default
+            }
+        };
+
+        Some(AttributeKind::Optimize(res, cx.attr_span))
+    }
+}