[Bug middle-end/323] optimized code gives strange floating point results

["vincent-gcc at vinc17 dot net" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=323

--- Comment #197 from Vincent Lefèvre <vincent-gcc at vinc17 dot net> ---
(In reply to Manuel López-Ibáñez from comment #196)
> Also, the official FAQ for this (https://gcc.gnu.org/bugs/#nonbugs_general)
> is seriously lacking info and outdated. From now on, I'll point people to:
> https://gcc.gnu.org/wiki/FAQ#PR323

Note that this bug was mainly about the excess precision of x87 FPU, though its
summary just says "optimized code gives strange floating point results". But
the users should be aware that the floating-point results can still depend on
the optimization level because this is allowed by the ISO C standard. For
instance, if one has code like x*y+z, a FMA can be used or not depending on the
target architecture and the optimization level (see also bug 37845 about this),
and this can change the results.

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