patch: rs6000 specific

[David Edelsohn]

>>>>> Dale Johannesen writes:

> Let's see if we can agree on the goal here.  Multiply-add generation
> is controlled by the -fno-fused-madd switch, as you said.  IMO when
> multiply-add generation is on (as it is by default) we should recognize
> as many mathematically correct cases of it as possible, without concern
> for IEEE compliance, since it's not compliant anyway.  I do not mean
> combine should behave this way, only the ppc-specific code.  This implies
> that we can't rely on combine to make IEEE-unsafe transformations;
> this needs to be done in the ppc-specific patterns.  Do you agree with
> this, and if not, what do you think the goal should be?

	I guess that I do not agree with this goal.  If GCC can generate
the transformations but only does them when -ffast-math is enabled, the
PowerPC backend should not duplicate those transformations.

David