flambda-backend: To upstream: flambda_o3 attribute support (includes bootstrap)

Author: mshinwell

boot/ocamlc

@@ -319,7 +319,16 @@ let clflags_attribute_without_payload attr ~name clflags_ref =
     | Some () -> clflags_ref := true
     | None -> ()
   end
-  
+
+let clflags_attribute_without_payload' attr ~name ~f =
+  if String.equal attr.attr_name.txt name
+    || String.equal attr.attr_name.txt ("ocaml." ^ name)
+  then begin
+    match parse_empty_payload attr with
+    | Some () -> f ()
+    | None -> ()
+  end
+
 let clflags_attribute_with_int_payload attr ~name clflags_ref =
   if String.equal attr.attr_name.txt name
     || String.equal attr.attr_name.txt ("ocaml." ^ name)
@@ -333,6 +342,14 @@ let nolabels_attribute attr =
   clflags_attribute_without_payload attr
     ~name:"nolabels" Clflags.classic
 
+let flambda_o3_attribute attr =
+  clflags_attribute_without_payload' attr
+    ~name:"flambda_o3"
+    ~f:(fun () ->
+      if Config.flambda then begin
+        Clflags.use_inlining_arguments_set Clflags.o3_arguments
+      end)
+
 let inline_attribute attr =
   if String.equal attr.attr_name.txt "inline"
     || String.equal attr.attr_name.txt "ocaml.inline"
@@ -363,4 +380,5 @@ let parse_standard_implementation_attributes attr =
   warning_attribute attr;
   nolabels_attribute attr;
   inline_attribute attr;
-  afl_inst_ratio_attribute attr
+  afl_inst_ratio_attribute attr;
+  flambda_o3_attribute attr

boot/ocamllex

@@ -30,6 +30,7 @@
     - ocaml.nolabels
     - ocaml.inline
     - ocaml.afl_inst_ratio
+    - ocaml.flambda_o3
 
     {b Warning:} this module is unstable and part of
   {{!Compiler_libs}compiler-libs}.