On Thu, 2015-09-10 at 19:55 +0200, Bernhard Reutner-Fischer wrote: > On September 10, 2015 7:48:10 PM GMT+02:00, David Edelsohn > <dje....@gmail.com> wrote: > >On Thu, Sep 10, 2015 at 1:41 PM, Bill Schmidt > ><wschm...@linux.vnet.ibm.com> wrote: > >> Currently the little-endian swap optimization is disabled for > >> computations that include vector permute instructions. We generate a > >> vperm in a variety of ways, and for the most general cases, we can't > >> replace a vperm with a swap-equivalent sequence without cost > >modeling. > >> However, the most common use of vperm is using an UNSPEC_VPERM where > >the > >> mask operand is loaded from the constant pool. For these cases, we > >can > >> optimize the computation provided that we change the loaded constant. > >> This patch recognizes these cases and provides the necessary special > >> handling. > >> > >> An abbreviated description of the general case being recognized is: > >> > >> (set (reg:DI A constant-pool-symbol)) > >> (set (reg:V16QI B (swap (mem:V16QI (reg:DI A))))) ; lxvd2x > >> (set (reg:V16QI C (swap (reg:V16QI B)))) ; xxpermdi > >> (set (reg D (unspec [(reg X)(reg Y)(reg:V16QI C)] UNSPEC_VPERM))) > >> > >> where "swap" is a vec_select operation that performs a doubleword > >swap. > >> We adjust the mask to be used and create a new constant pool entry > >for > >> it, with a new MEM used to load it. The new MEM is substituted into > >the > >> load instruction, after which cleanup is done on the dataflow > >> structures. > >> > >> I've added two new tests, one to verify that swaps are removed, and > >one > >> to verify that the vperm transformation produces correct results. > >> > >> Bootstrapped and tested on powerpc64le-unknown-linux-gnu with no > >> regressions. Is this ok for trunk? > > > >Okay. > > + if (!toc_relative_expr_p (SET_SRC (PATTERN (tocrel_insn)), false)) > + gcc_assert (0); > > Just curious if this isn't usually spelled as gcc_unreachable()? > Both should end up as equally unlikely I suppose so just bikeshedding..
Quite right, Bernhard! I'm apparently out of practice. ;) Will make that change. Bill > Thanks, >
