[llvm] [RegAlloc] Remove default restriction on non-trivial rematerialization (PR #159211)

[Reid Kleckner via llvm-commits]

rnk wrote:

I wanted to share that I think the reduction in reloads seemed promising, and @weiguozhi is benchmarking this change internally at Google. It's probably too early to say, and you can make what you will of our workloads, but we're seeing something between insignificant changes and improvements close to the noise threshold.

Clearly this is triggering superlinear register allocation behavior and that deserves to be investigated, but overall, thanks for revisiting this. 👍 

https://github.com/llvm/llvm-project/pull/159211