[optimizations] correct rewritting in conditionals for O3 (LB patch)

src/optimize_machine.ml

@@ -1020,10 +1020,12 @@ let add_ghost_assigns_reassigned rasg instrs =
  * ns the set of locations where it is written originally in SSA,
  * k the equation index where it is originally written,
  * b if there is a rewrite *)
-let add_assigned n k v =
+let add_assigned rasg n k v =
   VMap.update v (function
       | Some (ns, k', b) ->
-        if k = k' then Some (IntS.add n ns, k', b)
+        if rasg then
+          Some (ns, k', b || k > k' || not (IntS.mem n ns))
+        else if k = k' then Some (IntS.add n ns, k', b)
         else Some (ns, k', b || k > k')
       | None ->
         Some (IntS.singleton n, k, false))
@@ -1054,19 +1056,19 @@ let step_replace_var m reuse step =
   let step_checks =
     List.map (fun (l, v) -> l, value_replace_var fvar v) step.step_checks
   in
-  let rec asg_instr k (n, asg) instr =
+  let rec asg_instr rasg k (n, asg) instr =
     (* k: instruction block index (equation index)
      * n: instruction index (absolute) *)
     match instr.instr_desc with
     | MLocalAssign (i, v) ->
-      n + 1, if silly_asg i v then asg else add_assigned n k i asg
+      n + 1, if silly_asg i v then asg else add_assigned rasg n k i asg
     | MStep (il, _, _) ->
-      n + 1, List.fold_right (add_assigned n k) il asg
+      n + 1, List.fold_right (add_assigned rasg n k) il asg
     | MBranch (_, hl, _) ->
       let n, asg =
         List.fold_left
           (fun (n, asg) (_, il) ->
-            let n, asg = List.fold_left (asg_instr k) (n, asg) il in
+            let n, asg = List.fold_left (asg_instr rasg k) (n, asg) il in
             n, asg)
           (n, asg)
           hl
@@ -1075,10 +1077,10 @@ let step_replace_var m reuse step =
     | _ ->
       n + 1, asg
   in
-  let assigned asg instrs =
+  let assigned rasg asg instrs =
     let _, (_, asg) =
       List.fold_left
-        (fun (k, acc) i -> k + 1, asg_instr k acc i)
+        (fun (k, acc) i -> k + 1, asg_instr rasg k acc i)
         (0, (0, asg))
         instrs
     in
@@ -1087,20 +1089,20 @@ let step_replace_var m reuse step =
   (* SSA *)
   let step_instrs = add_ghost_assigns fvar step.step_instrs in
   (* register the locations of assignments *)
-  let asg = assigned VMap.empty step_instrs in
-  (* let pp fmt (ns, k, ks) = *)
+  let asg = assigned false VMap.empty step_instrs in
+  (* let pp fmt (ns, k, b) = *)
   (*   Format.( *)
-  (*     fprintf fmt "[%a]%n{@[%a}@]" *)
+  (*     fprintf fmt "[%a]%n:%a" *)
   (*       (pp_comma_list pp_print_int) (IntS.elements ns) *)
   (*       k *)
-  (*       (pp_comma_list pp_print_int) (IntS.elements ks)) *)
+  (*       pp_print_bool b) *)
   (* in *)
   (* Format.printf "AVANT %a@." (VMap.pp pp) asg; *)
   (* SSA *)
   let step_instrs = instrs_replace_var m fvar step_instrs in
   (* update the locations of assignments, consider as reassignments only the
      ones appearing *after* the original one *)
-  let asg = assigned asg step_instrs in
+  let asg = assigned true asg step_instrs in
   let rasg =
     VMap.filter_map
       (fun _ (ns, _, b) -> if b then Some ns else None)