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, 0 insertions, 1 deletions

diff --git a/backend/Renumber.v b/backend/Renumber.v
index 634fe56a..0a2c2f12 100644
--- a/backend/Renumber.v
+++ b/backend/Renumber.v
@@ -48,7 +48,6 @@ Definition renum_instr (i: instruction) : instruction :=
   | Icall sg ros args res s => Icall sg ros args res (renum_pc s)
   | Itailcall sg ros args => i
   | Ibuiltin ef args res s => Ibuiltin ef args res (renum_pc s)
-  | Iannot ef args s => Iannot ef args (renum_pc s)
   | Icond cond args s1 s2 => Icond cond args (renum_pc s1) (renum_pc s2)
   | Ijumptable arg tbl => Ijumptable arg (List.map renum_pc tbl)
   | Ireturn or => i