About llvm/benchmarks/

Kirill Bobyrev added the llvm/benchmarks/ directory in D50894 but the
directory does not draw people's attention after that.
Nick Terrell has a patch that improves SHA1 performance
⚙ D69295 Optimize SHA1 implementation and wants to add a benchmark file to
llvm/benchmarks/ .

Since llvm/benchmarks has never been used after the initial creation,
I want to bring up the topic about the usage of the directory.

What kind of benchmarks do we want? (Something that does not suite
test-suite repository.)
How shall we organize the directory structure?