[docs] Mention that we are in the process of removing the legacy PM for the optimization pipeline

[aeubanks]

Summary

And remove references to flags to turn it off.

[nikic]

clang/docs/ClangCommandLineReference.rst

4 ↗

(On Diff #422036)

See this line :)

[MaskRay]

clang/docs/ClangCommandLineReference.rst

910 ↗

(On Diff #422036)

This is generated by clang-tblgen. You can drop the help message from clang/include/clang/Driver/Options.td

[aeubanks]

remove help text instead of modifying generated docs

[aeubanks]

I tried regenerating ClangCommandLineReference.rst and it's a little out of date. I'll regenerate it in a separate change

[nikic]

LG

clang/include/clang/Driver/Options.td

defm jmc : BoolFOption<"jmc",
   PosFlag<SetTrue, [CC1Option], "Enable just-my-code debugging">,
   NegFlag<SetFalse>>;
 def fglobal_isel : Flag<["-"], "fglobal-isel">, Group<f_clang_Group>,
   HelpText<"Enables the global instruction selector">;
 def fexperimental_isel : Flag<["-"], "fexperimental-isel">, Group<f_clang_Group>,
   Alias<fglobal_isel>;
 defm legacy_pass_manager : BoolOption<"f", "legacy-pass-manager",
   CodeGenOpts<"LegacyPassManager">, DefaultFalse,
-  PosFlag<SetTrue, [], "Use the legacy pass manager in LLVM (deprecated, to be removed in a future release)">,
-  NegFlag<SetFalse, [], "Use the new pass manager in LLVM">,
+  PosFlag<SetTrue>,
+  NegFlag<SetFalse>,
   BothFlags<[CC1Option]>>, Group<f_clang_Group>;
 def fexperimental_new_pass_manager : Flag<["-"], "fexperimental-new-pass-manager">,
   Group<f_clang_Group>, Flags<[CC1Option]>, Alias<fno_legacy_pass_manager>;
 def fno_experimental_new_pass_manager : Flag<["-"], "fno-experimental-new-pass-manager">,
   Group<f_clang_Group>, Flags<[CC1Option,NoDriverOption]>, Alias<flegacy_pass_manager>;
 def fexperimental_strict_floating_point : Flag<["-"], "fexperimental-strict-floating-point">,
   Group<f_clang_Group>, Flags<[CC1Option]>,
   HelpText<"Enables experimental strict floating point in LLVM.">,

llvm/docs/NewPassManager.rst

 Status of the New and Legacy Pass Managers
 ==========================================
 
 LLVM currently contains two pass managers, the legacy PM and the new PM. The
 optimization pipeline (aka the middle-end) works with both the legacy PM and
 the new PM, whereas the backend target-dependent code generation only works
 with the legacy PM.
 
-For the optimization pipeline, the new PM is the default PM. The legacy PM is
-available for the optimization pipeline by setting various compiler/linker
-flags, e.g. ``-flegacy-pass-manager`` for ``clang``.
-
-There will be efforts to deprecate and remove the legacy PM for the
-optimization pipeline in the future.
+For the optimization pipeline, the new PM is the default PM. Using the legacy PM
+for the optimization pipeline is deprecated and there are ongoing efforts to
+remove its usage.
 
 Some IR passes are considered part of the backend codegen pipeline even if
 they are LLVM IR passes (whereas all MIR passes are codegen passes). This
 includes anything added via ``TargetPassConfig`` hooks, e.g.
 ``TargetPassConfig::addCodeGenPrepare()``. As mentioned before, passes added
 in ``TargetMachine::adjustPassManager()`` are part of the optimization
 pipeline, and should have a corresponding line in
 ``TargetMachine::registerPassBuilderCallbacks()``.
 
 Currently there are efforts to make the codegen pipeline work with the new
 PM.