[inferbo] More physical equalities for Bounds

Reviewed By: skcho

Differential Revision: D13176079

fbshipit-source-id: e09ebd176

infer/src/bufferoverrun/bounds.ml

@@ -41,6 +41,8 @@ module SymLinear = struct
 
   let le : t -> t -> bool =
    fun x y ->
+    phys_equal x y
+    ||
     let le_one_pair s v1_opt v2_opt =
       let v1 = NonZeroInt.opt_to_big_int v1_opt in
       let v2 = NonZeroInt.opt_to_big_int v2_opt in
@@ -82,13 +84,15 @@ module SymLinear = struct
   let plus : t -> t -> t =
    fun x y ->
     let plus_coeff _ c1 c2 = NonZeroInt.plus c1 c2 in
-    M.union plus_coeff x y
+    PhysEqual.optim2 x y ~res:(M.union plus_coeff x y)
 
 
-  let mult_const : NonZeroInt.t -> t -> t = fun n x -> M.map (NonZeroInt.( * ) n) x
+  let mult_const : NonZeroInt.t -> t -> t =
+   fun n x -> if NonZeroInt.is_one n then x else M.map (NonZeroInt.( * ) n) x
+
 
   let exact_div_const_exn : t -> NonZeroInt.t -> t =
-   fun x n -> M.map (fun c -> NonZeroInt.exact_div_exn c n) x
+   fun x n -> if NonZeroInt.is_one n then x else M.map (fun c -> NonZeroInt.exact_div_exn c n) x
 
 
   (* Returns a symbol when the map contains only one symbol s with a
@@ -445,8 +449,8 @@ module Bound = struct
         PInf
     | PInf ->
         MInf
-    | Linear (c, x) ->
+    | Linear (c, x) as b ->
-        Linear (Z.neg c, SymLinear.neg x)
+        if Z.(equal c zero) && SymLinear.is_zero x then b else Linear (Z.neg c, SymLinear.neg x)
     | MinMax (c, sign, min_max, d, x) ->
         mk_MinMax (Z.neg c, Sign.neg sign, min_max, d, x)
 
@@ -619,9 +623,15 @@ module Bound = struct
     overapprox_min original_b1 b2
 
 
-  let underapprox_max b1 b2 = neg (overapprox_min (neg b1) (neg b2))
+  let underapprox_max b1 b2 =
+    let res = neg (overapprox_min (neg b1) (neg b2)) in
+    if equal res b1 then b1 else if equal res b2 then b2 else res
+
+
+  let overapprox_max b1 b2 =
+    let res = neg (underapprox_min (neg b1) (neg b2)) in
+    if equal res b1 then b1 else if equal res b2 then b2 else res
 
-  let overapprox_max b1 b2 = neg (underapprox_min (neg b1) (neg b2))
 
   let approx_max = function
     | Symb.BoundEnd.LowerBound ->
@@ -678,11 +688,10 @@ module Bound = struct
 
   let plus_common : f:(t -> t -> t) -> t -> t -> t =
    fun ~f x y ->
+    if is_zero x then y
+    else if is_zero y then x
+    else
       match (x, y) with
-    | _, _ when is_zero x ->
-        y
-    | _, _ when is_zero y ->
-        x
       | Linear (c1, x1), Linear (c2, x2) ->
           Linear (Z.(c1 + c2), SymLinear.plus x1 x2)
       | MinMax (c1, sign, min_max, d1, x1), Linear (c2, x2)
@@ -723,6 +732,8 @@ module Bound = struct
 
   let mult_const : Symb.BoundEnd.t -> NonZeroInt.t -> t -> t =
    fun bound_end n x ->
+    if NonZeroInt.is_one n then x
+    else
       match x with
       | MInf ->
           if NonZeroInt.is_positive n then MInf else PInf
@@ -760,6 +771,8 @@ module Bound = struct
 
   let div_const : Symb.BoundEnd.t -> t -> NonZeroInt.t -> t option =
    fun bound_end x n ->
+    if NonZeroInt.is_one n then Some x
+    else
       match x with
       | MInf ->
           Some (if NonZeroInt.is_positive n then MInf else PInf)
@@ -803,10 +816,11 @@ module Bound = struct
 
   let is_not_infty : t -> bool = function MInf | PInf -> false | _ -> true
 
+  (** Substitutes ALL symbols in [x] with respect to [eval_sym]. Under/over-Approximate as good as possible according to [subst_pos]. *)
+  let subst : subst_pos:Symb.BoundEnd.t -> t -> eval_sym -> t bottom_lifted =
     let lift1 : (t -> t) -> t bottom_lifted -> t bottom_lifted =
      fun f x -> match x with Bottom -> Bottom | NonBottom x -> NonBottom (f x)
-
+    in
-
     let lift2 : (t -> t -> t) -> t bottom_lifted -> t bottom_lifted -> t bottom_lifted =
      fun f x y ->
       match (x, y) with
@@ -814,10 +828,7 @@ module Bound = struct
           Bottom
       | NonBottom x, NonBottom y ->
           NonBottom (f x y)
-
+    in
-
-  (** Substitutes ALL symbols in [x] with respect to [eval_sym]. Under/over-Approximate as good as possible according to [subst_pos]. *)
-  let subst : subst_pos:Symb.BoundEnd.t -> t -> eval_sym -> t bottom_lifted =
     fun ~subst_pos x eval_sym ->
       let get s =
         match eval_sym s with
@@ -847,6 +858,8 @@ module Bound = struct
       | MInf | PInf ->
           NonBottom x
       | Linear (c, se) ->
+          if SymLinear.is_empty se then NonBottom x
+          else
             SymLinear.fold se
               ~init:(NonBottom (of_big_int c))
               ~f:(fun acc s coeff -> lift2 (plus subst_pos) acc (get_mult_const s coeff))