[PATCH] Add a "no-split-stack" function attribute.

[Rafael Espíndola]

> Ok, I was taking a look at getting rid of EnableSegmentedStacks and just using
> a per-function split-stack attribute and I've run into a few places
> where that doesn't
> really work since we're not in the context of a function, like
> X86TargetLowering::resetOperationActions
> where it decides what to set the operation action for ISD:DYNAMIC_STACKALLOC.

I here you would have to always do:

    setOperationAction(ISD::DYNAMIC_STACKALLOC, Subtarget->is64Bit() ?
                       MVT::i64 : MVT::i32, Custom);

and then is the custom code you can decide what to do in a per function basis.

Cheers,
Rafael