[llvm] Add SPIRV lowering for intrinsics @llvm.fptosi.sat.* and @llvm.fptoui.sat.* (PR #125805)

[Eli Friedman via llvm-commits]

efriedma-quic wrote:

That looks like a bug in the prelegalizer: it should not be rewriting integers that way.  The legalizer itself should ensure only legal widths are used. If certain operations need to be rewritten early, the transform should be restricted to the operations in question.

Please fix the general issue here instead of working around the issue for G_FPTOSI_SAT specifically.

https://github.com/llvm/llvm-project/pull/125805