Re: [RFC] postreload cse'ing vector constants

[Robin Dapp <rdapp@linux.ibm.com>]

> Which is this from the mail archives:
> 
> https://gcc.gnu.org/pipermail/gcc-patches/1998-June/000308.html
> 
> I would tend to agree that for equal cost that the constant would be 
> preferred since that should be better from a scheduling/dependency 
> standpoint.   So it seems to me we can drive this purely from a costing 
> standpoint.

I did bootstrapping and ran the testsuite on x86(-64), aarch64, Power9
and s390.  Everything looks good except two additional fails on x86
where code actually looks worse.

gcc.target/i386/keylocker-encodekey128.c

17c17,18
<       movaps  %xmm4, k2(%rip)
---
>       pxor    %xmm0, %xmm0
>       movaps  %xmm0, k2(%rip)

gcc.target/i386/keylocker-encodekey256.c:

19c19,20
<       movaps  %xmm4, k3(%rip)
---
>       pxor    %xmm0, %xmm0
>       movaps  %xmm0, k3(%rip)

Regards
 Robin