[llvm] [PatternMatch] Allow `m_ConstantInt` to match integer splats (PR #153692)

[Luke Lau via llvm-commits]

lukel97 wrote:

> `m_ConstantInt` is intended to match a scalar. We may need a separate matcher to handle constant splats.

Whenever UseConstantIntForScalableSplat is enabled, and my understanding is that it will eventually be turned on by default, I think m_ConstantInt also matches constant splats?

I wonder if we should just put more focus on enabling it by default. Is there much work left to do? cc @paulwalker-arm

https://github.com/llvm/llvm-project/pull/153692