procyberian/gcc
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

Do not specify NAN sign in frange::set_nonnegative.

Browse source 
After further reading of the IEEE 754 standard, it has become clear
that there are no guarantees with regards to the sign of a NAN when it
comes to any operation other than copy, copysign, abs, and negate.

Currently, set_nonnegative() is only used in one place in ranger
applicable to floating point values, when expanding unknown calls.
Since we already specially handle copy, copysign, abs, and negate, all
the calls to set_nonnegative() must be NAN-sign agnostic.

The cleanest solution is to leave the sign unspecificied in
frange::set_nonnegative().  Any special case, must be handled by the
caller.

gcc/ChangeLog:

	* value-range.cc (frange::set_nonnegative): Remove NAN sign handling.
	(range_tests_signed_zeros): Adjust test.
This commit is contained in:
Aldy Hernandez 2022-11-10 14:29:13 +01:00
parent f1b76811f2
commit b4fc06d8c9
1 changed files with 7 additions and 5 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

12
gcc/value-range.cc
View file

@ -797,14 +797,17 @@ frange::zero_p () const
&& real_iszero (&m_max));
}
// Set the range to non-negative numbers, that is [+0.0, +INF].
//
// The NAN in the resulting range (if HONOR_NANS) has a varying sign
// as there are no guarantees in IEEE 754 wrt to the sign of a NAN,
// except for copy, abs, and copysign. It is the responsibility of
// the caller to set the NAN's sign if desired.
void
frange::set_nonnegative (tree type)
{
set (type, dconst0, frange_val_max (type));
// Set +NAN as the only possibility.
if (HONOR_NANS (type))
update_nan (/*sign=*/false);
}
// Here we copy between any two irange's. The ranges can be legacy or
@ -3923,7 +3926,6 @@ range_tests_signed_zeros ()
ASSERT_TRUE (r0.undefined_p ());
r0.set_nonnegative (float_type_node);
ASSERT_TRUE (r0.signbit_p (signbit) && !signbit);
if (HONOR_NANS (float_type_node))
ASSERT_TRUE (r0.maybe_isnan ());
}