[Bug middle-end/34678] Optimization generates incorrect code with -frounding-math option (#pragma STDC FENV_ACCESS not implemented)

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=34678

--- Comment #40 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Jakub Jelinek from comment #39)
> (In reply to Richard Biener from comment #36)
> > Created attachment 46396 [details]
> > poor mans solution^Whack

^^^^

> How does this work if op is a SSA_NAME?

it doens't, the patch has to be fixed to create a new def and adjust
all uses which isn't possible here (no immediate uses).

It's a proof-of-concept hack - the SSA name issue means we have to
find a better place for such hack.  Note I don't think we should
go with this kind of hack, iff, then we should at least not use
an ASM but some special __IFN and a more appropriate construct on
the RTL side (not sure what that would be).