[PATCH] [AVX512] [PR87767] Optimize memory broadcast for constant vector under AVX512

[Jakub Jelinek]

On Fri, Aug 28, 2020 at 12:36:00PM +0200, Richard Biener wrote:
> Guess this would work indeed.  It's probably quite common to have
> both vector and non-vector constants because of vectorization
> and scalar epilogues.  But note that elsewhere we're using
> the largest component mode to emit vector constant pool entries
> to share { -1, -1, -1, -1 } and {-1l, -1l } for example so while the
> below code works for FP modes it likely will break down for
> integer modes?

I don't see why it would break, it will not optimize { -1LL, -1LL }
vs. -1 scalar, sure, but it uses the hash and equality function the
rtl constant pool uses, which means it compares both the constants
(rtx_equal_p) and mode we have recorded for it.
Of course, on x86_64 integer scalar constants will pretty much never appear
in the constant pool, so guess we'll need a different target for testing
that.

	Jakub