Compiler: optmize cond more

Author: hhugo

compiler/lib/eval.ml

@@ -299,12 +299,39 @@ let the_case_of info x =
   | Pc (Tuple (j, _, _)) -> CTag j
   | _ -> Unknown
 
+type cond_of =
+  | Zero
+  | Non_zero
+  | Unknown
+
+let the_cond_of info x =
+  get_approx
+    info
+    (fun x ->
+      match info.info_defs.(Var.idx x) with
+      | Expr (Constant (Int 0l | Float 0.)) -> Zero
+      | Expr
+          (Constant
+            (Int _ | Float _ | Tuple _ | String _ | IString _ | Float_array _ | Int64 _))
+        ->
+          Non_zero
+      | Expr (Block (_, _, _)) -> Non_zero
+      | Expr (Field _ | Closure _ | Prim _ | Apply _) -> Unknown
+      | Param | Phi _ -> Unknown)
+    Unknown
+    (fun u v ->
+      match u, v with
+      | Zero, Zero -> Zero
+      | Non_zero, Non_zero -> Non_zero
+      | _ -> Unknown)
+    x
+
 let eval_branch info = function
   | Cond (x, ftrue, ffalse) as b -> (
-      match the_int info (Pv x) with
-      | Some 0l -> Branch ffalse
-      | Some _ -> Branch ftrue
-      | _ -> b)
+      match the_cond_of info x with
+      | Zero -> Branch ffalse
+      | Non_zero -> Branch ftrue
+      | Unknown -> b)
   | Switch (x, const, tags) as b -> (
       (* [the_case_of info (Pv x)] might be meaningless when we're inside a dead code.
          The proper fix would be to remove the deadcode entirely.