On Tue, Jun 21, 2016 at 06:46:57PM -0500, Bill Schmidt wrote: > >> When I did this, I ran into a problem with an existing test case. We end > >> up matching the *vsx_splat_v4si_internal pattern instead of falling back > >> to the altivec_vspltisw pattern. The constraints don't match for constant > >> input. To avoid this, I added a pattern ahead of this one that will match > >> for VMX output registers and produce the vspltisw as desired. This > >> corrected the failing test and produces the expected code. > > > > Why does the predicate allow constant input, while the constraints do not? > > I have no idea why it was built that way. The predicate seems to provide for > all sorts of things, but this and the subsequent pattern both handle only a > subset of the constraints implied by it. To be honest, I didn't feel > competent to try to fix the existing patterns. Do you have any suggestions > for what to do instead?
Don't give up so easily? ;-) The predicate should be tightened, the expander should use a new predicate that allows all those other things. The hardest part is figuring a good name for it ;-) Segher
