Re: [PATCH] Use signed boolean type for boolean vectors

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

On Mon, Nov 9, 2015 at 3:03 PM, Ilya Enkovich <enkovich.gnu@gmail.com> wrote:
> On 03 Nov 14:42, Richard Biener wrote:
>> On Wed, Oct 28, 2015 at 4:30 PM, Ilya Enkovich <enkovich.gnu@gmail.com> wrote:
>> > 2015-10-28 18:21 GMT+03:00 Richard Biener <richard.guenther@gmail.com>:
>> >> On Wed, Oct 28, 2015 at 2:13 PM, Ilya Enkovich <enkovich.gnu@gmail.com> wrote:
>> >>> Hi,
>> >>>
>> >>> Testing boolean vector conversions I found several runtime regressions
>> >>> and investigation showed it's due to incorrect conversion caused by
>> >>> unsigned boolean type.  When boolean vector is represented as an
>> >>> integer vector on target it's a signed integer actually.  Unsigned
>> >>> boolean type was chosen due to possible single bit values, but for
>> >>> multiple bit values it causes wrong casting.  The easiest way to fix
>> >>> it is to use signed boolean value.  The following patch does this and
>> >>> fixes my problems with conversion.  Bootstrapped and tested on
>> >>> x86_64-unknown-linux-gnu.  Is it OK?
>> >>
>> >> Hmm.  Actually formally the "boolean" vectors were always 0 or -1
>> >> (all bits set).  That is also true for a signed boolean with precision 1
>> >> but with higher precision what makes sure to sign-extend 'true'?
>> >>
>> >> So it's far from an obvious change, esp as you don't change the
>> >> precision == 1 case.  [I still think we should have precision == 1
>> >> for all boolean types]
>> >>
>> >> Richard.
>> >>
>> >
>> > For 1 bit precision signed type value 1 is out of range, right? This might break
>> > in many place due to used 1 as true value.
>>
>> For vectors -1 is true.  Did you try whether it breaks many places?
>> build_int_cst (type, 1) should still work fine.
>>
>> Richard.
>>
>
> I tried it and didn't find any new failures.  So looks I was wrong assuming it should cause many failures.  Testing is not complete because many SPEC benchmarks are failing to compile on -O3 for AVX-512 on trunk.  But I think we may proceed with signed type and fix constant generation issues if any revealed.  This patch was bootstrapped and regtested on x86_64-unknown-linux-gnu.  OK for trunk?

Ok.

Richard.

> Thanks,
> Ilya
> --
> gcc/
>
> 2015-11-09  Ilya Enkovich  <enkovich.gnu@gmail.com>
>
>         * optabs.c (expand_vec_cond_expr): Always get sign from type.
>         * tree.c (wide_int_to_tree): Support negative values for boolean.
>         (build_nonstandard_boolean_type): Use signed type for booleans.
>
>
> diff --git a/gcc/optabs.c b/gcc/optabs.c
> index fdcdc6a..44971ad 100644
> --- a/gcc/optabs.c
> +++ b/gcc/optabs.c
> @@ -5365,7 +5365,6 @@ expand_vec_cond_expr (tree vec_cond_type, tree op0, tree op1, tree op2,
>        op0a = TREE_OPERAND (op0, 0);
>        op0b = TREE_OPERAND (op0, 1);
>        tcode = TREE_CODE (op0);
> -      unsignedp = TYPE_UNSIGNED (TREE_TYPE (op0a));
>      }
>    else
>      {
> @@ -5374,9 +5373,9 @@ expand_vec_cond_expr (tree vec_cond_type, tree op0, tree op1, tree op2,
>        op0a = op0;
>        op0b = build_zero_cst (TREE_TYPE (op0));
>        tcode = LT_EXPR;
> -      unsignedp = false;
>      }
>    cmp_op_mode = TYPE_MODE (TREE_TYPE (op0a));
> +  unsignedp = TYPE_UNSIGNED (TREE_TYPE (op0a));
>
>
>    gcc_assert (GET_MODE_SIZE (mode) == GET_MODE_SIZE (cmp_op_mode)
> diff --git a/gcc/tree.c b/gcc/tree.c
> index 18d6544..6fb4c09 100644
> --- a/gcc/tree.c
> +++ b/gcc/tree.c
> @@ -1437,7 +1437,7 @@ wide_int_to_tree (tree type, const wide_int_ref &pcst)
>         case BOOLEAN_TYPE:
>           /* Cache false or true.  */
>           limit = 2;
> -         if (hwi < 2)
> +         if (IN_RANGE (hwi, 0, 1))
>             ix = hwi;
>           break;
>
> @@ -8069,7 +8069,7 @@ build_nonstandard_boolean_type (unsigned HOST_WIDE_INT precision)
>
>    type = make_node (BOOLEAN_TYPE);
>    TYPE_PRECISION (type) = precision;
> -  fixup_unsigned_type (type);
> +  fixup_signed_type (type);
>
>    if (precision <= MAX_INT_CACHED_PREC)
>      nonstandard_boolean_type_cache[precision] = type;