Re: [PATCH] Fix signed bitfield BIT_NOT_EXPR expansion (PR middle-end/52209)

[Richard Guenther <richard dot guenther at gmail dot com>]

On Sat, Feb 11, 2012 at 12:49 PM, Jakub Jelinek <jakub@redhat.com> wrote:
> Hi!
>
> In July Richard changed reduce_bit_field BIT_NOT_EXPR expansion from
> NOT unop to XOR with all the bits in the bitfield's precision set.
> Unfortunately that is correct for unsigned bitfields only, for signed
> bitfields, where op0 is already sign-extended to its mode before this,
> expanding this as NOT is the right thing.
>
> Fixed thusly, bootstrapped/regtested on x86_64-linux and i686-linux, ok for
> trunk?

Ok.

Thanks,
Richard.

> 2012-02-11 ?Jakub Jelinek ?<jakub@redhat.com>
>
> ? ? ? ?PR middle-end/52209
> ? ? ? ?* expr.c (expand_expr_real_2) <case BIT_NOT_EXPR>: Only expand using
> ? ? ? ?XOR for reduce_bit_field if type is unsigned.
>
> ? ? ? ?* gcc.c-torture/execute/pr52209.c: New test.
>
> --- gcc/expr.c.jj ? ? ? 2012-02-07 16:05:51.000000000 +0100
> +++ gcc/expr.c ?2012-02-11 10:08:44.162924423 +0100
> @@ -8582,8 +8582,9 @@ expand_expr_real_2 (sepops ops, rtx targ
> ? ? ? if (modifier == EXPAND_STACK_PARM)
> ? ? ? ?target = 0;
> ? ? ? /* In case we have to reduce the result to bitfield precision
> - ? ? ? ?expand this as XOR with a proper constant instead. ?*/
> - ? ? ?if (reduce_bit_field)
> + ? ? ? ?for unsigned bitfield expand this as XOR with a proper constant
> + ? ? ? ?instead. ?*/
> + ? ? ?if (reduce_bit_field && TYPE_UNSIGNED (type))
> ? ? ? ?temp = expand_binop (mode, xor_optab, op0,
> ? ? ? ? ? ? ? ? ? ? ? ? ? ? immed_double_int_const
> ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? (double_int_mask (TYPE_PRECISION (type)), mode),
> --- gcc/testsuite/gcc.c-torture/execute/pr52209.c.jj ? ?2012-02-11 10:09:46.080571803 +0100
> +++ gcc/testsuite/gcc.c-torture/execute/pr52209.c ? ? ? 2012-02-11 10:09:28.000000000 +0100
> @@ -0,0 +1,14 @@
> +/* PR middle-end/52209 */
> +
> +extern void abort (void);
> +struct S0 { int f2 : 1; } c;
> +int b;
> +
> +int
> +main ()
> +{
> + ?b = -1 ^ c.f2;
> + ?if (b != -1)
> + ? ?abort ();
> + ?return 0;
> +}
>
> ? ? ? ?Jakub