https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111694
--- Comment #4 from Andrew Macleod <amacleod at redhat dot com> ---
(In reply to Richard Biener from comment #3)
> Looks like some frange / relation mistake then.
l_3(D) [frange] double [-Inf, +Inf]
Equivalence set : [l_3(D), r_4(D)]
<bb 3> :
_1 = __builtin_signbit (l_3(D));
if (_1 != 0)
goto <bb 6>; [INV]
else
goto <bb 4>; [INV]
3->6 (T) _1 : [irange] int [-INF, -1][1, +INF]
3->6 (T) l_3(D) : [frange] double [-Inf, -0.0 (-0x0.0p+0)]
3->4 (F) _1 : [irange] int [0, 0]
3->4 (F) l_3(D) : [frange] double [0.0 (0x0.0p+0), +Inf]
<bb 4> :
_2 = __builtin_signbit (r_4(D));
Yeah, we know l_3 and r_4 are equivalent, and we also know that on the edge
3->4 l_3 has the range double [0.0 (0x0.0p+0), +Inf]
When we miss is that with an equivalence, we also have to put -0.0 back into
the range. We currently don't so we think we can fold the second signbit call.
If I fix that, we then see
r_4(D) [frange] double [-0.0 (-0x0.0p+0), +Inf]
which prevents the folding.
I need to audit to see if there are other places where we may have to "adjust"
equivalence range, or how best to deal with this in the general case.
