[sledge] Do not normalize shifts by enough bits to be undefined

Summary: Shifting by too many bits is undefined, so do not normalize them.

Reviewed By: mbouaziz

Differential Revision: D15098812

fbshipit-source-id: 96f4606d7

sledge/src/llair/exp.ml

@@ -1054,8 +1054,8 @@ let simp_xor x y =
 let simp_shl x y =
   match (x, y) with
   (* i shl j *)
-  | Integer {data= i; typ}, Integer {data= j} when Z.fits_int j ->
-      let bits = Option.value_exn (Typ.prim_bit_size_of typ) in
+  | Integer {data= i; typ= Integer {bits} as typ}, Integer {data= j}
+    when Z.sign j >= 0 && Z.lt j (Z.of_int bits) ->
       integer (Z.bshift_left ~bits i (Z.to_int j)) typ
   (* e shl 0 ==> e *)
   | e, Integer {data} when Z.equal Z.zero data -> e
@@ -1064,8 +1064,8 @@ let simp_shl x y =
 let simp_lshr x y =
   match (x, y) with
   (* i lshr j *)
-  | Integer {data= i; typ}, Integer {data= j} when Z.fits_int j ->
-      let bits = Option.value_exn (Typ.prim_bit_size_of typ) in
+  | Integer {data= i; typ= Integer {bits} as typ}, Integer {data= j}
+    when Z.sign j >= 0 && Z.lt j (Z.of_int bits) ->
       integer (Z.bshift_right_trunc ~bits i (Z.to_int j)) typ
   (* e lshr 0 ==> e *)
   | e, Integer {data} when Z.equal Z.zero data -> e
@@ -1074,8 +1074,8 @@ let simp_lshr x y =
 let simp_ashr x y =
   match (x, y) with
   (* i ashr j *)
-  | Integer {data= i; typ}, Integer {data= j} when Z.fits_int j ->
-      let bits = Option.value_exn (Typ.prim_bit_size_of typ) in
+  | Integer {data= i; typ= Integer {bits} as typ}, Integer {data= j}
+    when Z.sign j >= 0 && Z.lt j (Z.of_int bits) ->
       integer (Z.bshift_right ~bits i (Z.to_int j)) typ
   (* e ashr 0 ==> e *)
   | e, Integer {data} when Z.equal Z.zero data -> e