PR16752[PATCH]: 'mode' attribute for unusual targets doesn't work properly.

[Eli Friedman]

On Tue, Sep 3, 2013 at 2:16 AM, Stepan Dyatkovskiy <stpworld at narod.ru>wrote:

> Hi Eli,
> Sorry for latency.
> As you remember this patch should correct 'mode' attr implementation. You
> proposed to use generic way of type detection for each target: just scan
> for target types and select one with suitable width.
>
> Unfortunately I can't commit patch with generic implementation. I got test
> failure for clang. And I expect more failures for another targets. The
> reason is next.
>
> The target could still keep mode unsupported even if it has type of
> suitable width. I mean the next.
> For example this string should cause error for i686 machines (128 bit
> float):
> typedef          float f128ibm __attribute__ ((mode (TF)));
> But in case of generic approach for all targets it would be passed.
> In this case virtual functions allows to implement exceptions.
>

The generic implementation is still essentially correct; the the issue is
that getLongDoubleWidth() isn't actually the right value to check.  It
returns "sizeof(long double) * 8", not the actual width of the underlying
float format.  You should be able to work around this by
checking getLongDoubleFormat() instead of getLongDoubleWidth().

In this case 'getIntTypeByWidth' may be a bit confusing name. Instead it is
> supposed to return type for some particular mode, not by width. Something
> like getInt/RealTypeForMode(width, sign).
> Though, currently I kept the original name.
>
>
If you want to change it, that's fine.

-Eli
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