[llvm] [IR][AArch64] Add llvm.masked.speculative.load intrinsic (PR #156470)

[Graham Hunter via llvm-commits]

huntergr-arm wrote:

> It might be a good idea to split this patch up into two parts:
> 
> 1. A patch to introduce the LangRef and intrinsic along with the scalarisation code (on by default for all targets).
> 2. A follow-on patch to add the TTI hook and the codegen.
> 
> What do you think?

Yep, that's fine. I'll use this PR for the intrinsic and raise the AArch64 PR after this lands.

https://github.com/llvm/llvm-project/pull/156470