[PATCH, RFC] Remove unneeded HONOR_SIGNED_ZEROS from PowerPC FMA

[David Edelsohn <dje dot gcc at gmail dot com>]

Segher noticed some apparent unnecessary uses of HONOR_SIGNED_ZEROS in
the rs6000 port.  The original patch adding HONOR_SIGNED_ZEROS to the
final condition of some PowerPC FMA patterns applied it to patterns
with instructions that directly correspond to the RTL.  The RTL does
not change the grouping of the operands, so the setting of
HONOR_SIGNED_ZEROS should not matter.  When HONOR_SIGNED_ZEROS is
enabled, GCC canonicalizes RTL correctly for rs6000 and when
HONOR_SIGNED_ZEROS is disabled, the rs6000 port recognizes the
appropriate RTL.

My testing did not expose any problems with the patch, but I would
appreciate any feedback about the analysis and proposed patch.

Thanks, David

2009-11-11  Segher Boessenkool  <segher@kernel.crashing.org>

        * config/rs6000/rs6000.md (fnmaddsf4_powerpc_1): Remove
        HONOR_SIGNED_ZEROS final condition.
        (fnmsubsf4_powerpc_1): Same.
        (fnmadddf4_fpr_1): Same.
        (fnmsubdf4_fpr_1): Same.

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