[llvm] [VectorCombine][TTI] Disable Load Widening for SPIR-V (PR #227623)

[Simon Pilgrim via llvm-commits]

RKSimon wrote:

> > Can't you just adjust the costs with SPIRVTTIImpl::getMemoryOpCost?
> 
> Thanks for the prompt response!
> 
> I explored that possibility, but ultimately modeled this after #150216. Are you suggesting inserting an arbitrarily large cost for SPIR-V or something more detailed?

Yes, return InstructionCost::getInvalid() or something

https://github.com/llvm/llvm-project/pull/227623