https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102981
Aldy Hernandez <aldyh at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Ever confirmed|0 |1
Last reconfirmed| |2021-10-30
Status|UNCONFIRMED |NEW
--- Comment #1 from Aldy Hernandez <aldyh at gcc dot gnu.org> ---
In the pre-loop threaders (ethread, thread1, threadfull1), we can't touch
anything because it would cross loops, but by threadfull2 we should be able to.
There's a threadable path starting at the 2->6 edge here:
<bb 6> [local count: 118111600]:
# c_21 = PHI <c_30(5), 0(2)>
# ivtmp.16_8 = PHI <ivtmp.16_13(5), ivtmp.16_25(2)>
a.1_26 = a;
if (a.1_26 < 0)
goto <bb 12>; [89.00%]
else
goto <bb 10>; [11.00%]
but we don't because doing so would peel off an iteration. Hmmm, this is
really old code. I'm going to have to think about this:
// This is like path_crosses_loops in profitable_path_p but more
// restrictive, since profitable_path_p allows threading the
// first block because it would be redirected anyhow.
//
// If we loosened the restriction and used profitable_path_p()
// here instead, we would peel off the first iterations of loops
// in places like tree-ssa/pr14341.c.
