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Re: RFA: enable LRA for rs6000


On Fri, Apr 26, 2013 at 07:00:37PM -0400, Vladimir Makarov wrote:
> 2013-04-26  Vladimir Makarov  <vmakarov@redhat.com>
> 
>         * lra.c (setup_operand_alternative): Ignore '?'.
>         * lra-constraints.c (process_alt_operands): Print cost dump for
>         alternatives.  Check only moves for cycling.
>         (curr_insn_transform): Print insn name.

I'm not sure I'm comfortable with ignoring the '?' altogether.  For example, if
you do something in the GPR unit, instructions run at one cycle, while if you
do it in the vector unit, it runs in two cycles.  In the past, I've seen cases
where it wanted to spill floating point values from the floating point
registers to the CTR.  And if you spill to the LR, it can interfere with the
call cache.

Admitily, when to use '!', '?', and '*' is unclear, and unfortunately it has
changed over time.

-- 
Michael Meissner, IBM
IBM, M/S 2506R, 550 King Street, Littleton, MA 01460, USA
email: meissner@linux.vnet.ibm.com, phone: +1 (978) 899-4797


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