[PATCH] rs6000: Handle "d" output in the bd*z patterns (PR70098)

[David Edelsohn]

On Sat, Mar 12, 2016 at 8:55 AM, Segher Boessenkool
<segher@kernel.crashing.org> wrote:
> In the rs6000 port, FLOAT_REGS can contain DImode values when compiling
> for 64-bit targets.  Some instructions (like "fcfid" in the testcase,
> convert from integer to DP float) only work on floating point registers.
> So, we do want to allow DImode in these regs.
>
> Now, in unusual cases IRA will assign FLOAT_REGS to some allocno where
> some insns cannot handle FLOAT_REGS there, so they will need a reload.
> Maybe IRA can be made smarter, but it isn't doing anything wrong here,
> so we should be able to handle it.
>
> The place it goes wrong is in the output of the *ctrdi_internal[1256]
> pattern: the "bdz" and "bdnz" instructions.  GCC refuses to do output
> reloads on JUMP_INSNs, probably because it is hard to do, needs different
> strategies than "normal" reloads do, and it cannot even be done at all
> for general patterns.  So JUMP_INSNs need to be able to handle every
> possible output for the register class used.
>
> These patterns already handle writing to "c" (the base insn case), and
> to "r", "m", and "c" or "l"; all those via splitters.  We just need to
> handle "d" as well.  That is what this patch does.  [A predicate in one
> of the splitters needs to be touched up so that the correct splitter
> is used for the FLOAT_REGS case.]
>
> But, that leaves another problem.  One of the insns that are split to
> is a move from a GPR to an FPR.  That work fine on targets with direct
> move (which does exactly that), i.e. power8 and up.  But older targets
> need memory to do the move, and this splitter runs after reload so
> it cannot allocate memory; and allocating memory beforehand for every
> bdnz insn is pretty horrible as well.
>
> This patch implements the easy part.  With it, power8 works, where it
> didn't before.
>
> Tested on powerpc64-linux, -m32 and -m64, -mlra and -mno-lra.  Also
> regstrapping on a power8 powerpc64le-linux.  Is this okay for trunk
> if that works as expected?
>
>
> Segher
>
>
> 2016-03-12  Segher Boessenkool  <segher@kernel.crashing.org>
>
>         PR target/70098
>         * config/rs6000/rs6000.md (*ctr<mode>_internal1, *ctr<mode>_internal2,
>         *ctr<mode>_internal5, *ctr<mode>_internal6): Also allow "d" as output.
>         (define_split for the GPR case): Use int_reg_operand instead of
>         gpc_reg_operand for the output.
>
> gcc/testsuite/
>         PR target/70098
>         * g++.dg/pr70098.C: New testcase.

This is okay.

The testcase will need some XFAILs.

Thanks, David