From 3483ec72a1fc86461f70bbdf23986a52c4ea90b7 Mon Sep 17 00:00:00 2001
From: Josh Berdine <jjb@fb.com>
Date: Fri, 26 Apr 2019 12:03:29 -0700
Subject: [PATCH] [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 | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/sledge/src/llair/exp.ml b/sledge/src/llair/exp.ml
index cb8b40a64..ea8deefda 100644
--- a/sledge/src/llair/exp.ml
+++ b/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