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Do not clobber signbit when unioning a NAN. 

When unioning a known NAN and something else, we're dropping the
properties of the NAN, particularly the sign.  This fixes the
oversight.

With this patch, we should be keeping the sign bit up to date, even in
the presence of NANs.

gcc/ChangeLog:

	* value-range.cc (frange::union_): Do not drop properties when
	unioning a NAN with something else.
	(range_tests_signed_zeros): Add tests.
This commit is contained in:
Aldy Hernandez 2022-09-04 08:00:02 +02:00
parent 6832dd39d7
commit 8293a9632c
1 changed files with 21 additions and 4 deletions
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25
gcc/value-range.cc
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@ -475,19 +475,25 @@ frange::union_ (const vrange &v)
return true; return true;
} }
// If one side has a NAN, the union is just the other side plus the // If one side has a NAN, the union is the other side, plus the union
// NAN bit. // of the properties and the possibility of a NAN.
if (get_nan ().yes_p ()) if (get_nan ().yes_p ())
{ {
frange_props save = m_props;
*this = r; *this = r;
// NOP if NAN already set. m_props = save;
m_props.union_ (r.m_props);
set_nan (fp_prop::VARYING); set_nan (fp_prop::VARYING);
if (flag_checking)
verify_range ();
return true; return true;
} }
if (r.get_nan ().yes_p ()) if (r.get_nan ().yes_p ())
{ {
// NOP if NAN already set. m_props.union_ (r.m_props);
set_nan (fp_prop::VARYING); set_nan (fp_prop::VARYING);
if (flag_checking)
verify_range ();
return true; return true;
} }
@ -3676,6 +3682,7 @@ range_tests_signed_zeros ()
{ {
tree zero = build_zero_cst (float_type_node); tree zero = build_zero_cst (float_type_node);
tree neg_zero = fold_build1 (NEGATE_EXPR, float_type_node, zero); tree neg_zero = fold_build1 (NEGATE_EXPR, float_type_node, zero);
REAL_VALUE_TYPE q, r;
frange r0, r1; frange r0, r1;
// Since -0.0 == +0.0, a range of [-0.0, -0.0] should contain +0.0 // Since -0.0 == +0.0, a range of [-0.0, -0.0] should contain +0.0
@ -3711,6 +3718,16 @@ range_tests_signed_zeros ()
r1.set_signbit (fp_prop::YES); r1.set_signbit (fp_prop::YES);
r0.union_ (r1); r0.union_ (r1);
ASSERT_TRUE (r0.zero_p () && r0.get_signbit ().varying_p ()); ASSERT_TRUE (r0.zero_p () && r0.get_signbit ().varying_p ());
// NAN U [5,6] should be [5,6] with no sign info.
r0 = frange_nan (float_type_node);
r1 = frange_float ("5", "6");
r0.union_ (r1);
real_from_string (&q, "5");
real_from_string (&r, "6");
ASSERT_TRUE (real_identical (&q, &r0.lower_bound ()));
ASSERT_TRUE (real_identical (&r, &r0.upper_bound ()));
ASSERT_TRUE (r0.get_signbit ().varying_p ());
} }
static void static void