[llvm] [AMDGPU] Define constrained multi-dword scalar load instructions. (PR #96161)

[Christudasan Devadasan via llvm-commits]

cdevadas wrote:

> > > I also must say that s_buffer_load is in the same bucket.
> > 
> > 
> > Buffer loads are generated for the buffer intrinsic and we take care of them during legalization to always use natural alignment. But we might require the *_ec buffer opcodes for SILoadStoreOptimizer while merging them. @rampitec do you think that can happen?
> 
> It can happen I believe.

The buffer instructions aren't constrained yet. Can I do that in a separate patch?

https://github.com/llvm/llvm-project/pull/96161