lra incorrectly reloading scratch for a memory barrier?

[Jakub Jelinek]

On Fri, Jan 30, 2015 at 09:45:26AM -0800, Mike Stump wrote:
> I have a port that has:
> 
> (insn 47 46 48 18 (parallel [
>             (unspec_volatile:DI [
>                     (const_int 128 [0x80])
>                     (const_int 6 [0x6])
>                 ] UNSPECV_SPECIAL_OP)
>             (set (mem/v:BLK (scratch:DI) [0  A8])
>                 (unspec:BLK [
>                         (mem/v:BLK (scratch:DI) [0  A8])
>                     ] UNSPEC_MEMORY_BARRIER))

Why don't you just (clobber (mem/v:BLK (scratch:DI))) instead
of the second set in the parallel?  The instruction is already
UNSPEC_VOLATILE, and to make the barrier effect clear a clobber should be
sufficient.

	Jakub