[clang] [llvm] [RegAlloc] [X86] Enable callee saved register optimization for x86 (PR #188609)

[Wei Xiao via cfe-commits]

williamweixiao wrote:

@weiguozhi I've created an alternative PR to enable CSR optimization for all targets: https://github.com/llvm/llvm-project/pull/202007. The major difference from your approach is that it makes CSR cost configuration target-specific, since the cost is architecture-dependent and a global scaling option doesn't make sense. Even within the same target, different generations may have varying CSR costs. This allows each target to implement more fine-grained tuning as needed.
You can either enhance this patch further or allow my PR to land—both options work for me.

https://github.com/llvm/llvm-project/pull/188609