[PATCH] D67517: Create UsersManual section entitled 'Controlling Floating Point Behavior'

Fri Sep 13 14:40:19 PDT 2019

andrew.w.kaylor added inline comments.

================
Comment at: clang/docs/UsersManual.rst:1213
+
+.. option:: -f[no-]honor-nans
+
----------------
rjmccall wrote:
> andrew.w.kaylor wrote:
> > rjmccall wrote:
> > > cameron.mcinally wrote:
> > > > mibintc wrote:
> > > > > Both honor-nans and honor-infinities appear to have no effect at the moment, previously they were mapped to -menable-no-infs -menable-no-nans
> > > > I believe others have the same problem too. All probably need to be reassessed. E.g. I think -f[no-]trapping-math isn't hooked up to anything in LLVM.
> > > > 
> > > > This may also get confusing when the -fp-model=/etc options are added, since they really do the same thing in different ways.
> > > > 
> > > > Is there a plan in place for how to handle this? Will the GCC options alias the Clang options?
> > > If we accept these options, we should document them, even if just to say that they currently have no effect.  But I suspect that what this means is that they have no effect *separately* and we currently only enable NaN/Inf-unsafe optimizations given a more aggressive option like fast-math.
> > We have a fast-math flag for this (ninf and nnan). The front end should be connecting these options to those flags.
> Okay.  Let's keep this patch about documentation, and if we find semantic problems, we can address those in follow-ups.  So if these currently do nothing, we should document them that way.
Sounds good.

Repository:
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https://reviews.llvm.org/D67517