[clang] [llvm] [Mips] Add r5900 (PlayStation 2 Emotion Engine) CPU support (PR #176666)

[Rick Gaiser via cfe-commits]

================
@@ -5932,6 +5932,10 @@ def mcheck_zero_division : Flag<["-"], "mcheck-zero-division">,
 def mno_check_zero_division : Flag<["-"], "mno-check-zero-division">,
                               Group<m_mips_Features_Group>;
 def mfix4300 : Flag<["-"], "mfix4300">, Group<m_mips_Features_Group>;
+def mfix_r5900 : Flag<["-"], "mfix-r5900">, Group<m_mips_Features_Group>,
+  HelpText<"Enable R5900 short loop erratum fix">;
----------------
rickgaiser wrote:

"-mfix-r5900" and "-mno-fix-r5900" are chosen to be compatible with gcc:
https://gcc.gnu.org/onlinedocs/gcc-15.2.0/gcc/MIPS-Options.html

The `def` name equals the option name currently which is what most def's seem to do. So it currently seems correct to me.

I can give it a more descriptive name like `mfix5900_short_loop_bug` for instance but that will divert from how other def's are named? Unless we change the option name to match the def, but that would make llvm incompatible with gcc and is not desirable I think.

https://github.com/llvm/llvm-project/pull/176666