[llvm] [X86] Support EGPR (R16-R31) for APX (PR #67702)

[Shengchen Kan via llvm-commits]

KanRobert wrote:

> I have reverted this change, because it causes large compile-time regressions: http://llvm-compile-time-tracker.com/compare.php?from=b5dffd4957dfb58c73e168a3d9b6967f03b23a6c&to=feea5db01360b477b8cf2df03abfa9fc986633d5&stat=instructions%3Au
> 
> Please make sure that EGPR enablement does not materially affect compile-time for people who do not enable the EGPR target feature (= nearly everyone).

Thanks for the inform. Could I know how I can check if the updated patch may cause compile-time regression? @nikic 

https://github.com/llvm/llvm-project/pull/67702