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Re: [PATCH, rs6000] Generate LE code for vec_lvsl and vec_lvsr that is compatible with BE code
- From: Segher Boessenkool <segher at kernel dot crashing dot org>
- To: Bill Schmidt <wschmidt at linux dot vnet dot ibm dot com>
- Cc: gcc-patches at gcc dot gnu dot org, dje dot gcc at gmail dot com
- Date: Tue, 30 Sep 2014 15:37:22 -0500
- Subject: Re: [PATCH, rs6000] Generate LE code for vec_lvsl and vec_lvsr that is compatible with BE code
- Authentication-results: sourceware.org; auth=none
- References: <1412029574 dot 2986 dot 42 dot camel at gnopaine> <20140930145024 dot GB29948 at gate dot crashing dot org> <1412090663 dot 2986 dot 50 dot camel at gnopaine> <20140930160444 dot GC29948 at gate dot crashing dot org> <1412093919 dot 2986 dot 54 dot camel at gnopaine>
On Tue, Sep 30, 2014 at 11:18:39AM -0500, Bill Schmidt wrote:
> > I meant generating a sequence that just "falls out" as you want it after
> > optimisation. E.g. lvsr;vnot;vand(splat8(31));vperm can have the vand
> > absorbed by the vperm. But that splat is nasty when not optimised away :-(
>
> Especially since splat8(31) requires vsub(splat8(15),splat8(-16))...
vspltisb vT,-5 ; vsrb vD,vT,vT # :-)
> To get something that is correct with and without feeding a vperm and
> actually performs well just ain't happening here...
Yeah.
Segher