Re: gcc feature request / RFC: extra clobbered regs

[Vladimir Makarov]

On 07/01/2015 01:43 PM, Jakub Jelinek wrote:
> On Wed, Jul 01, 2015 at 01:35:16PM -0400, Vladimir Makarov wrote:
> > Actually it raise a question for me.  If we describe that a function
> > clobbers more than calling convention and then use it as a value (assigning
> > a variable or passing as an argument) and loosing a track of it and than
> > call it.  How can RA know what the call clobbers actually.  So for the
> > function with the attributes we should prohibit use it as a value or make
> > the attributes as a part of the function type, or at least say it is unsafe.
> > So now I see this as a *bigger problem* with this extension.  Although I
> > guess it already exists as we have description of different ABI as an
> > extension.
> Unfortunately target attribute is function decl attribute rather than
> function type.  And having more attributes affect switchable targets will be
> non-fun.
Making attributes a part of type probably creates a lot issues too.

Although I am not a front-end developer, still I think it is hard to 
implement in front-end.  Sticking fully to this approach, it would be 
logical to describe this as a debug info (I am not sure it is even 
possible).

Portability would be an issue too.  It is hard to prevent for a regular 
C developer to assign such function to variable because it is ok on his 
system while the compilation of such code may fail on another system.

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/