[llvm] [AArch64][GlobalISel] Take abs scalar codegen closer to SDAG (PR #84886)

[Madhur Amilkanthwar via llvm-commits]

madhur13490 wrote:

> > @arsenm @aemerson Given that there is a different approach now, do you still think `lower()` should be modified? If so, how do we reliably detect? Can you please elaborate a bit more?
> 
> Yes. Currently the lower implementation just calls lowerAbsToAddXor. You can conditionally call your new implementation based on isLegalOrCustom for the type with the relevant opcodes used in the expansion

I have updated. Please have a look. 

https://github.com/llvm/llvm-project/pull/84886