[PATCH] Fix PR55152

Richard Biener rguenther@suse.de
Tue Oct 4 13:23:00 GMT 2016


On Tue, 4 Oct 2016, Joseph Myers wrote:

> On Tue, 4 Oct 2016, Richard Biener wrote:
> 
> > Possibly.  Though then for FP we also want - abs (a) -> copysign (a, -1).
> 
> For architectures such as powerpc that have a negated-abs instruction, 
> does it get properly generated from the copysign code?  (The relevant 
> pattern in rs6000.md uses (neg (abs)) - is that the correct canonical RTL 
> for this?)

I have no idea - given that there is no copysign RTL code I suppose
it is the only machine independent RTL that can do this?

The question would be whether the copysign optab of said targets would
special-case the -1 case appropriately.

Given your comment I'm putting the copysign part of the patch on the side 
for now.  And I have to re-do the other part then.

Richard.



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