[PATCH] D106191: [clang] Option control afn flag

Erich Keane via Phabricator via cfe-commits cfe-commits at lists.llvm.org
Thu Oct 7 14:16:21 PDT 2021


erichkeane added inline comments.


================
Comment at: clang/docs/UsersManual.rst:1393
+
+   Allow substitution of approximate calculations for functions.
+   Defaults to ``-fno-approx-func``.
----------------
masoud.ataei wrote:
> erichkeane wrote:
> > This seems pretty incomplete to me, I have no idea what it does from this description.  Can you elaborate?
> If I didn't miss to say it is about math function calls, then I guess it would be more clear. 
> ```
> Allow substitution of approximate calculations for math function calls.
> ```
> This option just adds `afn` fast-math flag to the function calls and in backend the math function call can be replaced by an approximate calculation (either another math function call or not). 
> https://llvm.org/docs/LangRef.html#fast-math-flags
allow substitution of approximate calculations for math function with what?  I'm not clear as to what this does still.  I'm not sure that I get what the 'afn' documentation means there either.  Typically we'd want the clang frontend flags to be more accurate/descriptive than the LLVM-IR documentation.


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https://reviews.llvm.org/D106191



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