[clang] [Clang][x86]: allow PCLMULQDQ intrinsics to be used in constexpr (PR #169214)

[Ahmed Nour via cfe-commits]

ahmednoursphinx wrote:

> > waiting on fuzz test report
> 
> Hey @RKSimon sorry for being late on this but i had some issues as i mentioned that i work on a macbook with  silicon so i had to search for alternative and **godbolt** also executes PCLMULQDQ 256 bit instructions but couldn't execute cases for **VPCLMULQDQ** so i have managed to make it work with an **Amazon EC2** instance. So please find the test report here https://github.com/ahmednoursphinx/Clmul-Fuzzer/blob/main/vpclmulqdq_test_report.xlsx Also in the same report repository, you can find the generator scripts / modified [vpclmulqdq-builtins.c](https://github.com/ahmednoursphinx/Clmul-Fuzzer/blob/main/vpclmulqdq-builtins.c) / [Run time values](https://github.com/ahmednoursphinx/Clmul-Fuzzer/blob/main/ec2_test_results.txt) with more than 1000 cases
> 
> All tests passed successfully, and values matched 100%

Hey @RKSimon please check when you have some time 

https://github.com/llvm/llvm-project/pull/169214