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range-op-float: Only flush_denormals_to_zero for +-*/ [PR109154]

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As discussed in the PR, flushing denormals to zero on every frange::set
might be harmful for e.g. x < 0.0 comparisons, because we then on both
sides use ranges that include zero [-Inf, -0.0] on the true side, and
[-0.0, +Inf] NAN on the false side, rather than [-Inf, nextafter (-0.0, -Inf)]
on the true side.

The following patch does it only in range_operator_float::fold_range
which is right now used for +-*/ (both normal and reverse ops of those).

Though, I don't see any difference on the testcase in the PR, but not sure
what I should be looking at and the reduced testcase there has undefined
behavior.

2023-03-28  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/109154
	* value-range.h (frange::flush_denormals_to_zero): Make it public
	rather than private.
	* value-range.cc (frange::set): Don't call flush_denormals_to_zero
	here.
	* range-op-float.cc (range_operator_float::fold_range): Call
	flush_denormals_to_zero.
This commit is contained in:
Jakub Jelinek 2023-03-28 11:00:32 +02:00
parent 39a43dc336
commit ce3974e596
3 changed files with 3 additions and 3 deletions
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2
gcc/range-op-float.cc
View File

@ -112,6 +112,8 @@ range_operator_float::fold_range (frange &r, tree type,
}
}
r.flush_denormals_to_zero ();
return true;
}

2
gcc/value-range.cc
View File

@ -361,8 +361,6 @@ frange::set (tree type,
normalize_kind ();
flush_denormals_to_zero ();
if (flag_checking)
verify_range ();
}

2
gcc/value-range.h
View File

@ -373,6 +373,7 @@ public:
void update_nan (tree) = delete; // Disallow silent conversion to bool.
void update_nan (const nan_state &);
void clear_nan ();
void flush_denormals_to_zero ();
// fpclassify like API
bool known_isfinite () const;
@ -389,7 +390,6 @@ private:
bool union_nans (const frange &);
bool intersect_nans (const frange &);
bool combine_zeros (const frange &, bool union_p);
void flush_denormals_to_zero ();
tree m_type;
REAL_VALUE_TYPE m_min;