Re: [PATCH], Add IEEE 128-bit floating point to PowerPC, patch #1

[Michael Meissner <meissner at linux dot vnet dot ibm dot com>]

On Tue, Jun 02, 2015 at 01:43:08PM -0400, David Edelsohn wrote:
> Mike,
> 
> What is the purpose of the TARGET_LONG_DOUBLE_128 change in
> rs6000_hard_regno_mode_ok()?
> 
> +  /* If we don't allow 128-bit binary floating point, disallow the 128-bit
> +     types from going in any registers.  Similarly if __float128 is not
> +     supported, don't allow __float128/__ibm128 types.  */
> +  if (!TARGET_LONG_DOUBLE_128
> +      && (mode == TFmode || mode == KFmode || mode == IFmode))
> +    return false;
> 
> Why is this necessary now?

I was trying to avoid problems if there was no move/convert patterns for
KFmode/IFmode.  I made it when I transitioned from SPECIAL_FLOAT_MODE to
FRACTIONAL_FLOAT_MODE.  Given there are 2 fractional float modes now, if the
compiler was automatically trying to find a larger type than DFmode, it would
first try IFmode, then KFmode, and finally TFmode (under the old
SPECIAL_FLOAT_MODE, it wouldn't look at those types in the normal course of
things).

With the current set of patches, there is no move or convert options for
IFmode/KFmode, but also the emulator functions are not properly defined.

I can remove the lines and do the build again, if you would prefer.  I don't
think it is strictly necessary.

-- 
Michael Meissner, IBM
IBM, M/S 2506R, 550 King Street, Littleton, MA 01460-6245, USA
email: meissner@linux.vnet.ibm.com, phone: +1 (978) 899-4797