[patch AArch64] Do not perform a vector splat for vector initialisation if it is not useful

[Segher Boessenkool]

On Wed, May 16, 2018 at 11:10:55AM +0100, Kyrill Tkachov wrote:
> On 16/05/18 10:42, Richard Biener wrote:
> >Segher, do you know where canonicalization rules are documented?
> >IIRC we do not actively try to canonicalize in most cases.
> 
> The documentation we have for RTL canonicalisation is at:
> https://gcc.gnu.org/onlinedocs/gccint/Insn-Canonicalizations.html#Insn-Canonicalizations
> 
> It doesn't mention anything about vec_merge AFAICS so I couldn't convince 
> myself that there
> is a canonicalisation that we enforce (though maybe someone can prove me 
> wrong).

Many canonicalisations aren't documented, it's never clear which of the
canonicalisations are how canonical :-/


Segher