https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70935
--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
This is tree_unswitch_outer_loop -> hoist_guard not resetting debug stmts that
have some uses of SSA_NAMEs defined in the inner loop.
But the transformation is really weird.
We have:
loop7==================
bb10
|
v
loop2 =============
/>bb8
| inv test
| / |
| | something
| \ | \
| v v \
| bb7 +
| | |
+---+ |
loop2 end =========
|
v
bb13
DEBUG pm = defined_in_something
And we move the inv test to bb 10, with one edge going to loop2, and the other
to bb13 (newly added edge). If I understand the cfg right though, we've thus
changed an endless loop (if inv test is false, bb8 not really having any
side-effects just jumped to bb7 and back to bb8 forever) into no loop, and in
addition the newly added edge from bb10 to bb13 of course means any SSA_NAMEs
defined in loop2 can't be used.
