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

[Stepan Dyatkovskiy]

Since I had split the patch and committed only ASTContext and TargetInfo 
getIntTypeByWidth and friends, there is the second patch, that fixes 
PR16752 itself.

Please, find it in attachment for review.

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