On 9/20/23 11:12, Aldy Hernandez wrote:
In coming up with testcases for the unordered folders, I realized that
we were already handling them correctly, even in the absence of my
work in this area lately.
All of the unordered fold_range() methods try to fold with the ordered
variants first, and if they return TRUE, we are guaranteed to be able
to fold, even in the presence of NANs. For example:
if (x_5 >= y_8)
if (x_5 __UNLE y_8)
On the true side of the first conditional we know that either x_5 < y_8
or that one or more operands is a NAN. Since UNLE_EXPR returns true
for precisely this scenario, we can fold as true.
Ugh, that should've been the false edge of the first conditional, thus:
if (x_5 >= y_8)
{
}
else
{
// Relation at this point is: x_5 < y_8
// or either x_5 or y_8 is a NAN.
if (x_5 __UNLE y_8)
link_error();
}
The second conditional is foldable because LT U NAN is a subset of
__UNLE (which is LE U NAN).
The patch still stands though :).
Aldy
