https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96015
--- Comment #12 from Jeffrey A. Law <law at redhat dot com> ---
The block in question goes away because it serves no purpose:
<bb 5> [local count: 242478389]:
_13 = *self_11(D);
_16 = *other_12(D);
sign_17 = _13 - _16;
if (sign_17 == 0)
goto <bb 13>; [34.00%]
else
goto <bb 6>; [66.00%]
<bb 6> [local count: 160035736]:
goto <bb 13>; [100.00%]
Note that bb6 just transfers control to bb13 with no other side effects. As a
result bb5 is equivalent to:
<bb 5> [local count: 242478389]:
_13 = *self_11(D);
_16 = *other_12(D);
sign_17 = _13 - _16;
if (sign_17 == 0)
goto <bb 13>; [34.00%]
else
goto <bb 13>; [66.00%]
With both arms of the conditional going to the same place and no other uses of
sign_17 the whole block just turns into
goto <bb13>;
I see nothing wrong with what was done by DCE. The problem must be earlier in
the optimizer pipeline.
