Merge commit d2353ae00c3b from llvm git (by Argyrios Kyrtzidis):

[utils/TableGen/X86CompressEVEXTablesEmitter.cpp] Make sure the tablegen output for the `checkPredicate` function is deterministic (#84533)

The output for the `checkPredicate` function was depending on a
`std::map` iteration that was non-deterministic from run to run, because
the keys were pointer values.

Make a change so that the keys are `StringRef`s so the ordering is
stable.

This avoids non-determinism in llvm-tblgen output, which could cause
differences in the generated X86GenCompressEVEXTables.inc file. Although
these differences are not influencing the meaning of the generated code,
they still change a few bytes in libllvm. This in turn influences all
the binaries linked with libllvm, such as clang, ld.lld, etc.

Reported by: cperciva
MFC after: 3 days

(cherry picked from commit 7a8d05ba19b7762596c0ff22e668e4d50bac81cf)