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[Bug target/51340] SH Target: Make -mfused-madd enabled by default
- From: "oleg dot endo at t-online dot de" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: Mon, 19 Dec 2011 01:29:12 +0000
- Subject: [Bug target/51340] SH Target: Make -mfused-madd enabled by default
- Auto-submitted: auto-generated
- References: <bug-51340-4@http.gcc.gnu.org/bugzilla/>
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51340
--- Comment #2 from Oleg Endo <oleg.endo@t-online.de> 2011-12-19 01:29:12 UTC ---
(In reply to comment #1)
> (In reply to comment #0)
> > Is there any particular reason why this should not be enabled by
> > default for SH targets that support the FMAC insn?
>
> PR29100?
Uhm, yes...
The title should have been "Enable -mfused-madd by -ffast-math"
>
> BTW, if SH fmac satisfies the semantics for fused multiplication and
> add operation, the fmaf4 instruction pattern would be better now.
I don't know the exact semantics for the new patterns. All I know is that
rounding is supposed to be done only once after the two operations. This is
the case for the SH fmac insn. Not sure whether this is enough though.