On Fri, May 23, 2014 at 11:23 AM, Alan Modra <amo...@gmail.com> wrote:
> OK, let's start again from scratch. This patch fixes PR61098, a
> problem caused by trying to do arithmetic on the count register. The
> fix is to provide a new pseudo in rs6000_emit_set_long_const so
> arithmetic will be done in a gpr.
>
> Additionally, the patch fixes a number of other bugs and cleanup
> issues with rs6000_emit_set_{,long_}const.
>
> - rs6000_emit_set_long_const took two HWI constant parameters, a relic
> from the days when HWI might be 32 bits on powerpc. We're only
> setting a 64-bit value, so remove the unnecessary parameter.
>
> - The !TARGET_POWERPC64 handling of DImode assumed a 32 bit HWI, and
> the insn setting the low 32-bit reg was wrongly marked with a
> reg_equiv note saying the reg contained the entire 64-bit constant.
> I hadn't spotted the bad reg_equiv when writing the previous patch.
>
> - The comments describing the functions are inaccurate and misleading.
>
> - rs6000_emit_set_long_const always returns DEST, so it's caller can
> assume this and rs6000_emit_set_long_const return void.
>
> - The code testing for a NULL DEST in rs6000_emit_set_const is dead.
> DEST cannot be NULL, since the three uses of the function are in
> rs6000.md splitters where DEST (operand[0]) satisfies
> gpc_reg_operand.
>
> - The above two points mean that rs6000_emit_set_const always returns
> DEST, which in turn would allow rs6000_emit_set_const to return
> void. However, in view of a possible future change that might need
> to return status on whether rs6000_emit_set_const emitted anything,
> return a bool.
>
> - rs6000_emit_set_const parameter N is currently unused, and MODE
> always matches GET_MODE (DEST), so N and MODE can be removed.
>
> - The code is liberally sprinkled with copy_rtx. DEST/TEMP is always
> used once without copy_rtx, but which insn uses copy_rtx varies. I
> changed the code to always use a bare DEST as the last insn for
> consistency. (Writing the code this way might allow us to omit the
> copy_rtx on DEST/TEMP entirely. Before reload TEMP will be a new
> pseudo reg, thus doesn't need copy_rtx, and after reload we
> shouldn't have a SUBREG DEST. I wasn't sure of exactly what might
> happen during reload, so left well enough alone.)
>
> Bootstrapped and regression tested powerpc64-linux. OK to apply
> mainline?
This is a much clearer start. Thanks for the revised version.
This is okay.
Thanks, David
