llvm dev - Feb 2021 - Clang performance on ppc64le power8

Dear LLVM Developers,

The following are the performance comparisons on some different versions of
llvm I used to test my project (running openmp with 2 threads on Power8):

GCC/8.2.0 - host compiler:   17 Seconds
LLVM/12.0.0 - built with gcc/8.2.0:   27 Seconds
LLVM/11.0.0 - Downloaded Pre-built Binaries (PowerPC64LE Red Hat Enterprise
Linux
<https://github.com/llvm/llvm-project/releases/download/llvmorg-11.0.0/clang+llvm-11.0.0-powerpc64le-linux-rhel-7.4.tar.xz>):
27 Seconds
LLVM/8.0.1 -  Downloaded Pre-built Binaries (   Red Hat Enterprise Linux
7.4 ppc64le
<https://github.com/llvm/llvm-project/releases/download/llvmorg-8.0.1/clang+llvm-8.0.1-powerpc64le-linux-rhel-7.4.tar.xz>
):
 17 Seconds

It is surprising to find that the older version of llvm/8.0.1 reaches its
performance that is close to gcc/8.2.0, while the newer are almost twice as
slower than gcc/8.2.0.
Any idea about these low performances of newer versions?

Best Regards,
Shelton
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