Be more precise for << of Intervals

src/cdomains/intDomain.ml

@@ -610,6 +610,11 @@ module IntervalArith(Ints_t : IntOps.IntOps) = struct
     let x2y2 = (Ints_t.mul x2 y2) in
     (min4 x1y1 x1y2 x2y1 x2y2, max4 x1y1 x1y2 x2y1 x2y2)
 
+  let shiftleft (x1,x2) (y1,y2) =
+    let y1p = Ints_t.shift_left Ints_t.one y1 in
+    let y2p = Ints_t.shift_left Ints_t.one y2 in
+    mul (x1, x2) (y1p, y2p)
+
   let div (x1, x2) (y1, y2) =
     let x1y1n = (Ints_t.div x1 y1) in
     let x1y2n = (Ints_t.div x1 y2) in
@@ -851,7 +856,6 @@ struct
 
   let bitnot = bit1 (fun _ik -> Ints_t.bitnot)
   let shift_right = bitcomp (fun _ik x y -> Ints_t.shift_right x (Ints_t.to_int y))
-  let shift_left  = bitcomp (fun _ik x y -> Ints_t.shift_left  x (Ints_t.to_int y))
 
   let neg ?no_ov ik = function None -> (None,{underflow=false; overflow=false}) | Some x -> norm ik @@ Some (IArith.neg x)
 
@@ -864,6 +868,20 @@ struct
   let mul ?no_ov = binary_op_with_norm IArith.mul
   let sub ?no_ov = binary_op_with_norm IArith.sub
 
+  let shift_left ik a b =
+    match is_bot a, is_bot b with
+    | true, true -> (bot_of ik,{underflow=false; overflow=false})
+    | true, _
+    | _   , true -> raise (ArithmeticOnIntegerBot (Printf.sprintf "%s op %s" (show a) (show b)))
+    | _ ->
+      match a, maximal b, minimal b with
+      | Some a, Some bl, Some bu when (Ints_t.compare bl Ints_t.zero >= 0) ->
+        (try
+           let r = IArith.shiftleft a (Ints_t.to_int bl, Ints_t.to_int bu) in
+           norm ik @@ Some r
+         with Z.Overflow -> (top_of ik,{underflow=false; overflow=true}))
+      | _              -> (top_of ik,{underflow=true; overflow=true})
+
   let rem ik x y = match x, y with
     | None, None -> None
     | None, _ | _, None -> raise (ArithmeticOnIntegerBot (Printf.sprintf "%s op %s" (show x) (show y)))

tests/regression/39-signed-overflows/06-shiftleft.c

@@ -0,0 +1,23 @@
+// PARAM: --enable ana.int.interval
+#include <goblint.h>
+int main()
+{
+    int r;
+    int zero_or_one = 0;
+    int top;
+    char c;
+    r = c << 1U; //NOWARN
+
+    r = c << 128U; //WARN
+    r = r << 1U; //WARN
+    r = 8 << -2; //WARN
+
+    if(top) { zero_or_one = 1; }
+
+    r = 8 << zero_or_one;
+
+    __goblint_check(r >= 8);
+    __goblint_check(r <= 16);
+
+    return 0;
+}