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Re: [RS6000] cost SLOW_UNALIGNED_ACCESS


On Wed, Aug 03, 2016 at 12:05:07AM +0930, Alan Modra wrote:
> As noted in the last patch, rs6000_rtx_costs ought to cost slow
> unaligned mems.  This stops combine merging loads/stores with a
> mode-changing SET subreg, if the load/store in the subreg mode would
> be slow.  Costing slow mems at 100 insns is just an order of magnitude
> estimate.  (The alignment interrupt does cost quite a lot.
> Experiments on power8 with a misaligned lwarx showed taking the
> alignment interrupt cost roughly 300 insns.)

Okay for trunk.  Do you have a testcase, too?


Segher


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