[LLVMdev] Structs as first class values.

[Richard Pennington]

Matthijs Kooijman wrote:
> On this topic, you should look at the StructRetPromotion pass
> (lib/Transforms/IPO/StructRetPromotion.cpp). This pass does exactly the
> opposite of what you propose: It transforms return pointers in the first
> parameter to first class returns.
> 
> This pass only operates on internal functions, though, so it does not have to
> deal with ABI issues. If you want to support the C ABI (which requires a
> pointer in the first argument to return any struct AFAIK), you might be better
> off generating such code in your frontend. Any internal function can then be
> simplified by the sretpromotion pass (perhaps it could be modified to take an
> option for the maximum number of elements to put in the real return struct?)

Hi Matthijs,

Thanks for the pointer. It was the first time I looked at an LLVM pass 
closely. Very nice and simple!

I think I will have my frontend pass the pointer. I can always back it 
out when return values are handled. Although it might be fun to try to 
implement a StructRetDemotion pass. ;-)

-Rich