https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91683
Jim Wilson <wilson at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Last reconfirmed| |2019-09-06
CC| |wilson at gcc dot gnu.org
Assignee|unassigned at gcc dot gnu.org |wilson at gcc dot
gnu.org
Ever confirmed|0 |1
--- Comment #1 from Jim Wilson <wilson at gcc dot gnu.org> ---
Created attachment 46850
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=46850&action=edit
proposed fix
This is failing in undo_all in combine, trying to write to a pointer into data
that has been garbage collected.
The problem starts with a riscv.md splitter which calls riscv_move_integer
which checks can_create_pseudo_p and calls force_reg if allowed. This
eventually calls gen_reg_rtx which calls ensure_regno_capacity which calls
ggc_realloc, which invalidates the data in the undo buffer since all pseudo reg
addresses change. I guess this is another reason why calling gen_reg_rtx in a
splitter is a bad idea.
I can fix it by adding another option to riscv_move_integer to indicate when we
are calling it from inside a splitter, but maybe I will think of a better way
to fix the problem later.
The fact that this requires a ggc_realloc call to happen in a very precise
place means that this testcase does not appear to be very useful. There is no
guarantee it will trigger the problem if other parts of the compiler change.
