[llvm] [GlobalISel][ARM] Legalization of G_CONSTANT using constant pool (PR #98308)

[Amara Emerson via llvm-commits]

aemerson wrote:

> > This is the wrong approach. Please reconsider #96225. We loose the `.legalFor`. #97513 showed issues with `.customFor` . There are less constants in the pipeline. AArch64 shows
> > https://github.com/llvm/llvm-project/blob/fec1b6f9d3cf5347b67ffb2078c995eb496acf47/llvm/lib/Target/AArch64/GISel/AArch64InstructionSelector.cpp#L2580
> 
> Disagree. AArch64 should remove this custom handling. This is not how the DAG
> 
> > how to handle constant pool loads in the selector.
> > Gisel has a type-based legalizer. There are no illegal values.
> 
> Not exactly, legal means can be selected. It doesn't mean custom cannot add restrictions. We could also always augment legality with immediate values (like we already do for sext_inreg)

(truncated reply?) I'm not following what the issue is here.

https://github.com/llvm/llvm-project/pull/98308