On Thu, 1 Sep 2022, Joseph Myers wrote:
On Thu, 1 Sep 2022, FX via Gcc wrote:
A tentative patch is attached, it seems to work well on simple examples,
but for test coverage the hard part is going to be that the comparisons
seem to be optimised away very easily into their non-signaling versions.
Basically, if I do:
Presumably that can be reproduced without depending on the new built-in
function? In which case it's an existing bug somewhere in the optimizers.
(simplify
(cmp @0 REAL_CST@1)
[...]
(if (REAL_VALUE_ISNAN (TREE_REAL_CST (@1))
&& !tree_expr_signaling_nan_p (@1)
&& !tree_expr_maybe_signaling_nan_p (@0))
{ constant_boolean_node (cmp == NE_EXPR, type); })
only tries to preserve a comparison with sNaN, but not with qNaN. There
are probably other issues since various gcc devs used to have a different
opinion on the meaning of -ftrapping-math.
--
Marc Glisse
