scanon added inline comments.
================ Comment at: clang/docs/LanguageExtensions.rst:3182 +enabled for the translation unit with the ``-fassociative-math`` flag. +The pragma can take two values: ``on`` and ``off``. + ---------------- mibintc wrote: > scanon wrote: > > rjmccall wrote: > > > Do you want to add an example here? > > Is the intention that this allows reassociation only within statements > > (like fp contract on)? Based on the ir in the tests, I think the answer is > > "no". > > > > If so, should "on" be called "fast" instead, since its semantics match the > > "fast" semantics for contract, and reserve "on" for reassociation within a > > statement (that seems like it would also be useful, potentially)? > > > > Otherwise, please add some tests with multiple statements. > > > > I agree with John that `pragma clang fp reassociate` is a reasonable > > spelling. > The intention is that the pragma can be placed at either file scope or at the > start of a compound statement, if at file scope it affects the functions > following the pragma. If at compound statement it is effective for the > compound statement, i can modify the test to have multiple statements. I > disagree with the suggestion of "fast" instead of on/off. at the command > line you can use -f[no-]associative-math; of course that command line option > isn't specific to floating point, but the point is it's on/off ; i can't > speak to whether "fast" would be a useful setting. Thanks for your review I don't think you understood my comment, so I'll try to explain more clearly: I am not asking if it applies to multiple statements or a single statement; I am asking within what scope reassociation is allowed. An example: `fp contract on` allows: ``` double r = a*b + c; ``` to be contracted to an fma, but does not allow: ``` double t = a*b; double r = t + c; ``` to be contracted. `fp contract fast` allows both to be contracted. Your reassociate pragma, if I am understanding correctly, allows: ``` double t = a + b; double r = t + c; ``` to be reassociated; this matches the behavior of `fp contract fast`. I am asking if, for the sake of understandability and orthogonality of the floating-point model, it would make more sense for this option to be named `fast`, reserving `on` for a mode that only allows reassociation within expressions. Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D78827/new/ https://reviews.llvm.org/D78827 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
