[LLVMdev] Troubling promotion of return value to Integer ...

[Chris Lattner]

On Mon, 19 May 2008 Alireza.Moshtaghi at microchip.com wrote:
> Correction:
>
> The analysis I made regarding the callers knowledge of sign/zero
> extension of return value is flawed. So I take it back.
>
> Never the less, I don't see how adding attributes would resolve this
> problem either.

Ok, I'm not sure what issue you mean.  Can you restate?

-Chris

> ________________________________
>
> From: llvmdev-bounces at cs.uiuc.edu [mailto:llvmdev-bounces at cs.uiuc.edu]
> On Behalf Of Alireza.Moshtaghi at microchip.com
> Sent: Sunday, May 18, 2008 6:33 PM
> To: llvmdev at cs.uiuc.edu
> Subject: Re: [LLVMdev] Troubling promotion of return value to Integer
> ...
>
>
>
> But they both follow the same calling convention. There are two
> possibilities in the caller:
>
> 1) Call node returns sizeof(int) or larger: in this case there is no
> truncation.
>
> 2) Call node returns smaller than sizeof(int): in this case callee
> always has to return an int so it has to consistently either sign extend
> or zero extend because int is either signed or unsigned consistently for
> that port. Assuming that caller and callee follow the same calling
> convention, caller always knows (hence the llvm pass knows) that, if the
> return value of the called function is being truncated, it is because of
> return value promotion. It also knows the calling convention, so it
> knows whether it is sign or zero extended. This is regardless of
> translation unit where the callee is in.
>
>
>
>> No, because the callee and caller may be in different translation
> units.
>
>

-Chris

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