[Bug target/33135] [SH] -ffinite-math-only should not be on by default

["olegendo at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33135

Oleg Endo <olegendo at gcc dot gnu.org> changed:

           What    |Removed                     |Added
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                 CC|                            |olegendo at gcc dot gnu.org

--- Comment #1 from Oleg Endo <olegendo at gcc dot gnu.org> 2012-07-15 20:08:49 UTC ---
(In reply to comment #0)
> The documentation of -ffinite-math-only states
> "This option should never be turned on by any '-O' option"
> 
> but for sh's -mieee it is said "the default is set to -ffinite-math-only"
> (-mieee is unset by default)
> 
> as a result the -ffinite-math-only is turned on by default for the sh for all
> optimisation levels.
> 
> on chapter 2 it was reenforced that: ... "*By default*, it (gcc) will act as
> the compiler for a hosted implementation" ... and a conforming hosted
> implementation 
> supports the whole standard.
> 
> So either the documentation is false or infinite float values should be
> supported (by default).
> The ability to perform optimum floating point code is preserved by explicitly
> setting it.

The SH -mieee option documentation is wrong.
-ffinite-math-only is not enabled by default (maybe it used to be some time
ago?).  Thus, -mieee is enabled by default (and -mno-ieee has no effect).

Moreover, the documentation part 
"... getting IEEE-conforming results for comparisons of NANs / infinities
incurs extra overhead in every floating-point comparison..."

is confusing, because this is not what the compiler actually does.  If I
observe correctly, the only cases where two fcmp instructions are generated are
when doing '>=' or '<=' comparisons.

I would suggest to make the -mieee option control only the FPU comparisons and
not make it change the flag_finite_math_only.  Also support for -mno-ieee
should be added.