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[range-op-float] Set NAN possibility for INF + (-INF) and vice versa.

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Some combinations of operations can yield a NAN even if no operands
have the possiblity of a NAN.  For example, [-INF] + [+INF] = NAN and
vice versa.

For [-INF,+INF] + [-INF,+INF], frange_arithmetic will not return a
NAN, and since the operands have no possibility of a NAN, we will
mistakenly assume the result cannot have a NAN.  This fixes the
oversight.

gcc/ChangeLog:

	* range-op-float.cc (foperator_plus::fold_range): Set NAN for
	addition of different signed infinities.
	(range_op_float_tests): New test.
This commit is contained in:
Aldy Hernandez 2022-11-08 23:42:04 +01:00
parent b305793b98
commit 68b0615be2
1 changed files with 25 additions and 1 deletions
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26
gcc/range-op-float.cc
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@ -1863,7 +1863,21 @@ foperator_plus::fold_range (frange &r, tree type,
r.set (type, lb, ub);
if (lb_nan || ub_nan)
// Some combinations can yield a NAN even if no operands have the
// possibility of a NAN.
bool maybe_nan;
// [-INF] + [+INF] = NAN
if (real_isinf (&op1.lower_bound (), true)
&& real_isinf (&op2.upper_bound (), false))
maybe_nan = true;
// [+INF] + [-INF] = NAN
else if (real_isinf (&op1.upper_bound (), false)
&& real_isinf (&op2.lower_bound (), true))
maybe_nan = true;
else
maybe_nan = false;
if (lb_nan || ub_nan || maybe_nan)
// Keep the default NAN (with a varying sign) set by the setter.
;
else if (!op1.maybe_isnan () && !op2.maybe_isnan ())
@ -1960,6 +1974,16 @@ range_op_float_tests ()
r1 = frange_float ("-1", "-0");
r1.update_nan (false);
ASSERT_EQ (r, r1);
// [-INF,+INF] + [-INF,+INF] could be a NAN.
range_op_handler plus (PLUS_EXPR, float_type_node);
r0.set_varying (float_type_node);
r1.set_varying (float_type_node);
r0.clear_nan ();
r1.clear_nan ();
plus.fold_range (r, float_type_node, r0, r1);
if (HONOR_NANS (float_type_node))
ASSERT_TRUE (r.maybe_isnan ());
}
} // namespace selftest