poly_int: ira subreg liveness tracking
Normmaly the IRA-reload interface tries to track the liveness of
individual bytes of an allocno if the allocno is sometimes written
to as a SUBREG. This isn't possible for variable-sized allocnos,
but it doesn't matter because targets with variable-sized registers
should use LRA instead.
This patch adds a get_subreg_tracking_sizes function for deciding
whether it is possible to model a partial read or write. Later
patches make it return false if anything is variable.
2017-12-20 Richard Sandiford <richard.sandiford@linaro.org>
Alan Hayward <alan.hayward@arm.com>
David Sherwood <david.sherwood@arm.com>
gcc/
* ira.c (get_subreg_tracking_sizes): New function.
(init_live_subregs): Take an integer size rather than a register.
(build_insn_chain): Use get_subreg_tracking_sizes. Update calls
to init_live_subregs.
git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@255881
138bc75d-0d04-0410-961f-
82ee72b054a4