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

[David Edelsohn <dje dot gcc at gmail dot com>]

On Tue, Jun 2, 2015 at 2:27 PM, Michael Meissner
<meissner@linux.vnet.ibm.com> wrote:
> 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.

The first patch is okay.  This clearly is going to require a lot of
interations with libgcc and GLIBC.

Thanks, David