[PATCH rs6000] Fix PR target/84369: gcc.dg/sms-10.c fails on Power9

[Segher Boessenkool]

Hi Pat,

On Mon, Apr 15, 2019 at 03:43:26PM -0500, Pat Haugen wrote:
> As pointed out in the PR, the test is failing because a store->load dependency is reporting zero cost. Fixed by leaving existing costs as is (i.e. cost for update forms), and just adding a simple bypass for store->load dependencies.

Cool, wildcards in the define_bypass.  Nice trick :-)

My only worry is this does not catch *all* loads and stores (larx and stcx
not, at least).  But it is not necessary for correctness, so okay.

> Bootstrap/regtest on powerpc64le (Power9) with no new regressions and testcase now passing. Also ran cpu2006/cpu2017 benchmark comparisons with no notable differences. Ok for trunk?

Yes please.  Backports are okay, too, if you think we should have those.
Thanks!


Segher


> 2019-04-15  Pat Haugen  <pthaugen@us.ibm.com>
> 
> 	PR target/84369
> 	* config/rs6000/power9.md: Add store forwarding bypass.