https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102895
Aldy Hernandez <aldyh at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
Resolution|--- |DUPLICATE
CC| |law at gcc dot gnu.org,
| |matz at gcc dot gnu.org
--- Comment #3 from Aldy Hernandez <aldyh at gcc dot gnu.org> ---
This is *almost* a duplicate of PR102981.
Here we have the same scenario: the first iteration of a loop has unreachable
code. But interestingly, the IL is sufficiently simple that DOM3 (post
loopdone) can see the threading opportunity:
a.c.192t.dom3: [3] Registering jump thread: (2, 3) incoming edge; (3, 4)
normal;
but... there's some limitation in the custom block copier the old forward
threader uses:
a.c.192t.dom3:Failure in thread_through_loop_header: Cancelling jump thread:
(2, 3) incoming edge; (3, 4) normal;
Again, the backward threader will refuse to thread this, regardless of
loopdone, because it is essentially peeling off the first iteration of a loop.
This is the main issue we should address, regardless of DOM's limitation.
I'm going to mark this as a duplicate, because I doubt anyone has the
inclination of fixing the old forward threader's copier.
[FWIW, this supersedes the previous comment I made for this PR, as the threader
pipeline has changed in trunk.]
*** This bug has been marked as a duplicate of bug 102981 ***
