[PATCH] D82756: Port some floating point options to new option marshalling infrastructure

[Jan Svoboda via Phabricator via cfe-commits]

jansvoboda11 added a comment.

Thanks for the feedback Duncan.

I don't think this patch introduces any changes the parser. We only change the way how  `CodeGenOpts` and `LangOpts` get populated when using `DefaultAnyOf<[...]>`. I've added a test of `CompilerInvocation` that checks just that.



================
Comment at: clang/include/clang/Driver/Options.td:1176
+defm reciprocal_math : OptInFFlag< "reciprocal-math", "Allow division operations to be reassociated", "", "", [], "LangOpts->AllowRecip">;
+def fapprox_func : Flag<["-"], "fapprox-func">, Group<f_Group>, Flags<[CC1Option, NoDriverOption]>,
+  MarshallingInfoFlag<"LangOpts->ApproxFunc", "false">;
----------------
dexonsmith wrote:
> dang wrote:
> > Anastasia wrote:
> > > could this also be OptInFFlag?
> > The aim was to keep the driver semantics the same as before and this was not something you could control with the driver, so I left it as just a CC1 flag. However if it makes sense to be able to control this from the driver then we can definitely make this `OptInFFLag`.
> I think adding a driver flag (if that's the right thing to do) should be done separately in a follow-up commit.
> 
> Also for a separate commit: it would be a great improvement if you could have OptIn / OptOut flags that were `-cc1`-only (maybe `CC1OptInFFlag`).
> - Both `-fX` and `-fno-X` would be parsed by `-cc1` (and cancel each other out).
> - Only the non-default one would be generated when serializing to `-cc1` from `CompilerInvocation` (for `OptIn`, we'd never generate `-fno-X`).
> - Neither would be recognized by the driver.
> 
> I suggest we might want that for most `-cc11` flags. This would make it easier to poke through the driver with `-Xclang` to override `-cc1` options the driver adds. Not something we want for end-users, but useful for debugging the compiler itself. Currently the workflow is to run the driver with `-###`, copy/paste, search for and remove the option you want to skip, and finally run the `-cc1` command...
> 
> The reason I bring it up is that it's possible people will start using `OptInFFLag` just in order to get this behaviour, not because they intend to add a driver flag.
I agree that making all `OptInFFlag` and `OptOutFFlag` driver flags as well as `-cc1` flags by default is not great. How would we go about deciding which options are okay to demote to `-cc1`-only? Perhaps those not present in `ClangCommandLineReference.rst` and driver invocations in tests?


================
Comment at: clang/lib/Frontend/CompilerInvocation.cpp:3707
 #undef OPTION_WITH_MARSHALLING_FLAG
+
   return true;
----------------
dexonsmith wrote:
> I don't have an opinion about whether there should be a newline here, but please make unrelated whitespace changes like this in a separate commit (before/after).
Got it.


================
Comment at: llvm/utils/TableGen/OptParserEmitter.cpp:460-464
+    if (AID < BID)
+      return -1;
+    if (AID > BID)
+      return 1;
+    return 0;
----------------
dexonsmith wrote:
> I think `array_pod_sort` will use this like a `bool`, similar to `std::sort`, in which case you I think you want:
> ```
>   return (*A)->getID() < (*B)->getID();
> ```
I see that `array_pod_sort` calls `qsort` from the C standard library, which should use the result of comparator as an `int`.


================
Comment at: llvm/utils/TableGen/OptParserEmitter.cpp:468-469
+  // Restore the definition order of marshalling options.
+  array_pod_sort(OptsWithMarshalling.begin(), OptsWithMarshalling.end(),
+                 CmpMarshallingOpts);
+
----------------
dexonsmith wrote:
> I'm curious if this is necessary. If so, how do the options get out-of-order?
> 
> Also, a cleaner way to call `array_pod_sort` would be:
> ```
> llvm::sort(OptsWithMarshalling, CmpMarshallingOpts);
> ```
> and I would be tempted to define the lambda inline in the call to `llvm::sort`.
> 
> If it's not necessary, I suggest replacing with an assertion:
> ```
> assert(llvm::is_sorted(OptsWithMarshalling, ...));
> ```
1. The options get out of order during parsing. The `RecordKeeper` stores records in `std::map<std::string, std::unique_ptr<Record>, std::less<>>` that maintains lexicographical order.

2. Later, they are reordered in this function before prefix groups are generated: `array_pod_sort(Opts.begin(), Opts.end(), CompareOptionRecords);`.

3. Before we generate the marshalling code, we need to restore the definition order so that we don't use a `LangOpts` or `CodeGenOpts` field (from `DefaultAnyOf`) before it was initialized.

I've added more detailed explanation to the comment.

I used `array_pod_sort` to be consistent with what's already used here in `OptParserEmitter.cpp`. I will switch to `llvm::sort` to be more concise if we don't mind the potential code bloat described here <https://llvm.org/doxygen/namespacellvm.html#add1eb5637dd671428b6f138ed3db6428>.


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https://reviews.llvm.org/D82756