Refactoring of builtins and annotations in the back-end.

Before, the back-end languages had distinct instructions
- Iannot for annotations, taking structured expressions (annot_arg)
  as arguments, and producing no results'
- Ibuiltin for other builtins, using simple pseudoregs/locations/registers
  as arguments and results.

This branch enriches Ibuiltin instructions so that they take structured
expressions (builtin_arg and builtin_res) as arguments and results.
This way,
- Annotations fit the general pattern of builtin functions,
  so Iannot instructions are removed.
- EF_vload_global and EF_vstore_global become useless, as the
  same optimization can be achieved by EF_vload/vstore taking
  a structured argument of the "address of global" kind.
- Better code can be generated for builtin_memcpy between stack locations,
  or volatile accesses to stack locations.

Finally, this commit also introduces a new kind of external function,
EF_debug, which is like EF_annot but produces no observable events.
It will be used later to transport debug info through the back-end,
without preventing optimizations.

1 files changed, 2 insertions, 3 deletions

diff --git a/backend/Splitting.ml b/backend/Splitting.ml
index 53600c98..97b26a50 100644
--- a/backend/Splitting.ml
+++ b/backend/Splitting.ml
@@ -162,9 +162,8 @@ let ren_instr f maps pc i =
   | Itailcall(sg, ros, args) ->
       Itailcall(sg, ren_ros before ros, ren_regs before args)
   | Ibuiltin(ef, args, res, s) ->
-      Ibuiltin(ef, ren_regs before args, ren_reg after res, s)
-  | Iannot(ef, args, s) ->
-      Iannot(ef, List.map (AST.map_annot_arg (ren_reg before)) args, s)
+      Ibuiltin(ef, List.map (AST.map_builtin_arg (ren_reg before)) args,
+                   AST.map_builtin_res (ren_reg after) res, s)
   | Icond(cond, args, s1, s2) ->
       Icond(cond, ren_regs before args, s1, s2)
   | Ijumptable(arg, tbl) ->