Merge pull request rust-lang#141 from rust-lang/fix/unsigned-by-signed-shift

Fix shift of unsigned integer by signed integer

Author: antoyo

src/int.rs

@@ -68,14 +68,9 @@ impl<'a, 'gcc, 'tcx> Builder<'a, 'gcc, 'tcx> {
         let a_native = self.is_native_int_type(a_type);
         let b_native = self.is_native_int_type(b_type);
         if a_native && b_native {
-            // FIXME(antoyo): remove the casts when libgccjit can shift an unsigned number by an unsigned number.
+            // FIXME(antoyo): remove the casts when libgccjit can shift an unsigned number by a signed number.
             // TODO(antoyo): cast to unsigned to do a logical shift if that does not work.
-            if a_type.is_unsigned(self) && b_type.is_signed(self) {
-                let a = self.context.new_cast(None, a, b_type);
-                let result = a >> b;
-                self.context.new_cast(None, result, a_type)
-            }
-            else if a_type.is_signed(self) && b_type.is_unsigned(self) {
+            if a_type.is_signed(self) != b_type.is_signed(self) {
                 let b = self.context.new_cast(None, b, a_type);
                 a >> b
             }

tests/run/int.rs

@@ -71,6 +71,8 @@ fn main(argc: isize, _argv: *const *const u8) -> isize {
     assert_eq!(var3 << (argc + 62) as u128, 96618259944854013731572476686437974016);
     assert_eq!(var3 << (argc + 63) as u128, 193236519889708027463144953372875948032);
 
+    assert_eq!((2220326408_u32 + argc as u32) >> (32 - 6), 33);
+
     assert_eq!(var >> (argc as u128 - 1), var);
     assert_eq!(var >> argc as u128, 67108928);
     assert_eq!(var >> (argc + 32) as u128, 0);