On Thu, Sep 22, 2022 at 6:49 PM Aldy Hernandez <al...@redhat.com> wrote:
>
> Similarly to how we drop NANs to UNDEFINED when -ffinite-math-only, I
> think we can drop the numbers outside of the min/max representable
> numbers to the representable number.
>
> This means the endpoings to VR_VARYING for -ffinite-math-only can now
> be the min/max representable, instead of -INF and +INF.
>
> Saturating in the setter means that the upcoming implementation for
> binary operators no longer have to worry about doing the right
> thing for -ffinite-math-only. If the range goes outside the limits,
> it'll get chopped down.
>
> How does this look?
>
> Tested on x86-64 Linux.
>
> gcc/ChangeLog:
>
> * range-op-float.cc (build_le): Use vrp_val_*.
> (build_lt): Same.
> (build_ge): Same.
> (build_gt): Same.
> * value-range.cc (frange::set): Chop ranges outside of the
> representable numbers for -ffinite-math-only.
> (frange::normalize_kind): Use vrp_val*.
> (frange::verify_range): Same.
> (frange::set_nonnegative): Same.
> (range_tests_floats): Remove tests that depend on -INF and +INF.
> * value-range.h (real_max_representable): Add prototype.
> (real_min_representable): Same.
> (vrp_val_max): Set max representable number for
> -ffinite-math-only.
> (vrp_val_min): Same but for min.
> (frange::set_varying): Use vrp_val*.
> ---
> gcc/range-op-float.cc | 12 +++++++----
> gcc/value-range.cc | 46 ++++++++++++++++++++-----------------------
> gcc/value-range.h | 30 ++++++++++++++++++++++------
> 3 files changed, 53 insertions(+), 35 deletions(-)
>
> diff --git a/gcc/range-op-float.cc b/gcc/range-op-float.cc
> index 2bd3dc9253f..15ba19c2deb 100644
> --- a/gcc/range-op-float.cc
> +++ b/gcc/range-op-float.cc
> @@ -232,7 +232,8 @@ build_le (frange &r, tree type, const frange &val)
> {
> gcc_checking_assert (!val.known_isnan ());
>
> - r.set (type, dconstninf, val.upper_bound ());
> + REAL_VALUE_TYPE ninf = *TREE_REAL_CST_PTR (vrp_val_min (type));
> + r.set (type, ninf, val.upper_bound ());
>
> // Add both zeros if there's the possibility of zero equality.
> frange_add_zeros (r, type);
> @@ -257,7 +258,8 @@ build_lt (frange &r, tree type, const frange &val)
> return false;
> }
> // We only support closed intervals.
> - r.set (type, dconstninf, val.upper_bound ());
> + REAL_VALUE_TYPE ninf = *TREE_REAL_CST_PTR (vrp_val_min (type));
> + r.set (type, ninf, val.upper_bound ());
> return true;
> }
>
> @@ -268,7 +270,8 @@ build_ge (frange &r, tree type, const frange &val)
> {
> gcc_checking_assert (!val.known_isnan ());
>
> - r.set (type, val.lower_bound (), dconstinf);
> + REAL_VALUE_TYPE inf = *TREE_REAL_CST_PTR (vrp_val_max (type));
> + r.set (type, val.lower_bound (), inf);
>
> // Add both zeros if there's the possibility of zero equality.
> frange_add_zeros (r, type);
> @@ -294,7 +297,8 @@ build_gt (frange &r, tree type, const frange &val)
> }
>
> // We only support closed intervals.
> - r.set (type, val.lower_bound (), dconstinf);
> + REAL_VALUE_TYPE inf = *TREE_REAL_CST_PTR (vrp_val_max (type));
> + r.set (type, val.lower_bound (), inf);
> return true;
> }
>
> diff --git a/gcc/value-range.cc b/gcc/value-range.cc
> index 7e8028eced2..e57d60e1bac 100644
> --- a/gcc/value-range.cc
> +++ b/gcc/value-range.cc
> @@ -338,6 +338,18 @@ frange::set (tree min, tree max, value_range_kind kind)
> m_neg_nan = false;
> }
>
> + // For -ffinite-math-only we can drop ranges outside the
> + // representable numbers to min/max for the type.
> + if (flag_finite_math_only)
> + {
> + REAL_VALUE_TYPE min_repr = *TREE_REAL_CST_PTR (vrp_val_min (m_type));
> + REAL_VALUE_TYPE max_repr = *TREE_REAL_CST_PTR (vrp_val_max (m_type));
> + if (real_less (&m_min, &min_repr))
> + m_min = min_repr;
> + if (real_less (&max_repr, &m_max))
> + m_max = max_repr;
I think you want to re-formulate that in terms of real_isinf() and
change those to the max representable values.
> + }
> +
> // Check for swapped ranges.
> gcc_checking_assert (tree_compare (LE_EXPR, min, max));
>
> @@ -371,8 +383,8 @@ bool
> frange::normalize_kind ()
> {
> if (m_kind == VR_RANGE
> - && real_isinf (&m_min, 1)
> - && real_isinf (&m_max, 0))
> + && vrp_val_is_min (build_real (m_type, m_min))
> + && vrp_val_is_max (build_real (m_type, m_max)))
I think this suggests that keeping +-Inf might be the better choice.
At least you want to change vrp_val_is_min/max to take a REAL_VALUE_TYPE
to avoid building four tree nodes for just this compare?
> {
> if (m_pos_nan && m_neg_nan)
> {
> @@ -385,8 +397,8 @@ frange::normalize_kind ()
> if (!m_pos_nan || !m_neg_nan)
> {
> m_kind = VR_RANGE;
> - m_min = dconstninf;
> - m_max = dconstinf;
> + m_min = *TREE_REAL_CST_PTR (vrp_val_min (m_type));
> + m_max = *TREE_REAL_CST_PTR (vrp_val_max (m_type));
> return true;
> }
> }
> @@ -706,8 +718,8 @@ frange::verify_range ()
> case VR_VARYING:
> gcc_checking_assert (m_type);
> gcc_checking_assert (m_pos_nan && m_neg_nan);
> - gcc_checking_assert (real_isinf (&m_min, 1));
> - gcc_checking_assert (real_isinf (&m_max, 0));
> + gcc_checking_assert (vrp_val_is_min (build_real (m_type, m_min)));
> + gcc_checking_assert (vrp_val_is_max (build_real (m_type, m_max)));
> return;
> case VR_RANGE:
> gcc_checking_assert (m_type);
> @@ -732,7 +744,8 @@ frange::verify_range ()
> // If all the properties are clear, we better not span the entire
> // domain, because that would make us varying.
> if (m_pos_nan && m_neg_nan)
> - gcc_checking_assert (!real_isinf (&m_min, 1) || !real_isinf (&m_max, 0));
> + gcc_checking_assert (!vrp_val_is_min (build_real (m_type, m_min))
> + || !vrp_val_is_max (build_real (m_type, m_max)));
> }
>
> // We can't do much with nonzeros yet.
> @@ -779,7 +792,7 @@ frange::zero_p () const
> void
> frange::set_nonnegative (tree type)
> {
> - set (type, dconst0, dconstinf);
> + set (type, dconst0, *TREE_REAL_CST_PTR (vrp_val_max (type)));
>
> // Set +NAN as the only possibility.
> if (HONOR_NANS (type))
> @@ -3886,23 +3899,6 @@ range_tests_floats ()
> r0.clear_nan ();
> ASSERT_FALSE (r0.varying_p ());
>
> - // The endpoints of a VARYING are +-INF.
> - r0.set_varying (float_type_node);
> - ASSERT_TRUE (real_identical (&r0.lower_bound (), &dconstninf));
> - ASSERT_TRUE (real_identical (&r0.upper_bound (), &dconstinf));
> -
> - // The maximum representable range for a type is still a subset of VARYING.
> - REAL_VALUE_TYPE q, r;
> - real_min_representable (&q, float_type_node);
> - real_max_representable (&r, float_type_node);
> - r0 = frange (float_type_node, q, r);
> - // r0 is not a varying, because it does not include -INF/+INF.
> - ASSERT_FALSE (r0.varying_p ());
> - // The upper bound of r0 must be less than +INF.
> - ASSERT_TRUE (real_less (&r0.upper_bound (), &dconstinf));
> - // The lower bound of r0 must be greater than -INF.
> - ASSERT_TRUE (real_less (&dconstninf, &r0.lower_bound ()));
> -
> // For most architectures, where float and double are different
> // sizes, having the same endpoints does not necessarily mean the
> // ranges are equal.
> diff --git a/gcc/value-range.h b/gcc/value-range.h
> index 3668b331187..74879b76b40 100644
> --- a/gcc/value-range.h
> +++ b/gcc/value-range.h
> @@ -593,6 +593,8 @@ extern void dump_value_range (FILE *, const vrange *);
> extern bool vrp_val_is_min (const_tree);
> extern bool vrp_val_is_max (const_tree);
> extern bool vrp_operand_equal_p (const_tree, const_tree);
> +inline void real_max_representable (REAL_VALUE_TYPE *r, const_tree type);
> +inline void real_min_representable (REAL_VALUE_TYPE *r, const_tree type);
>
> inline value_range_kind
> vrange::kind () const
> @@ -1009,7 +1011,15 @@ vrp_val_max (const_tree type)
> return wide_int_to_tree (const_cast<tree> (type), max);
> }
> if (frange::supports_p (type))
> - return build_real (const_cast <tree> (type), dconstinf);
> + {
> + if (flag_finite_math_only)
> + {
> + REAL_VALUE_TYPE r;
> + real_max_representable (&r, type);
> + return build_real (const_cast <tree> (type), r);
> + }
> + return build_real (const_cast <tree> (type), dconstinf);
Overall there's too many places affected IMHO. The above also shows
we're building trees a lot - note that REAL_CST are _not_ shared, so
each time you call build_real a new REAL_CST tree node is allocated
(and later GCed if no longer used).
I thought vrp_val_min/max are legacy by now ...
That said, using trees for the range representation might not be the
very best thing to do, it's unnecessarily wrapping things.
> + }
> return NULL_TREE;
> }
>
> @@ -1023,7 +1033,15 @@ vrp_val_min (const_tree type)
> if (POINTER_TYPE_P (type))
> return build_zero_cst (const_cast<tree> (type));
> if (frange::supports_p (type))
> - return build_real (const_cast <tree> (type), dconstninf);
> + {
> + if (flag_finite_math_only)
> + {
> + REAL_VALUE_TYPE r;
> + real_min_representable (&r, type);
> + return build_real (const_cast <tree> (type), r);
> + }
> + return build_real (const_cast <tree> (type), dconstninf);
> + }
> return NULL_TREE;
> }
>
> @@ -1073,8 +1091,8 @@ frange::set_varying (tree type)
> {
> m_kind = VR_VARYING;
> m_type = type;
> - m_min = dconstninf;
> - m_max = dconstinf;
> + m_min = *TREE_REAL_CST_PTR (vrp_val_min (type));
> + m_max = *TREE_REAL_CST_PTR (vrp_val_max (type));
> m_pos_nan = true;
> m_neg_nan = true;
> }
> @@ -1133,7 +1151,7 @@ frange::clear_nan ()
> // Set R to maximum representable value for TYPE.
>
> inline void
> -real_max_representable (REAL_VALUE_TYPE *r, tree type)
> +real_max_representable (REAL_VALUE_TYPE *r, const_tree type)
> {
> char buf[128];
> get_max_float (REAL_MODE_FORMAT (TYPE_MODE (type)),
> @@ -1145,7 +1163,7 @@ real_max_representable (REAL_VALUE_TYPE *r, tree type)
> // Set R to minimum representable value for TYPE.
>
> inline void
> -real_min_representable (REAL_VALUE_TYPE *r, tree type)
> +real_min_representable (REAL_VALUE_TYPE *r, const_tree type)
> {
> real_max_representable (r, type);
> *r = real_value_negate (r);
> --
> 2.37.1
>
