[llvm] r179026 - Generate PPC early conditional returns

[Hal Finkel]

----- Original Message -----
> From: "Krzysztof Parzyszek" <kparzysz at codeaurora.org>
> To: "Hal Finkel" <hfinkel at anl.gov>
> Cc: llvm-commits at cs.uiuc.edu
> Sent: Tuesday, April 9, 2013 12:14:59 PM
> Subject: Re: [llvm] r179026 - Generate PPC early conditional returns
> 
> On 4/9/2013 12:07 PM, Hal Finkel wrote:
> >
> > I think that early if conversion is too early because it happens
> > before epilogue generation.
> 
> Does this cause a problem?
> Early return can help avoid a PHI node in the return block, and can
> expose opportunity for shrink-wrapping.

I'd think so; because I can only predicate the blr, not anything else related to the epilogue (like restoring registers, stack pointer, etc.) the epilogue being 'predicated' must be trivial. We won't know whether or not it will be trivial until PEI+Target generates the epilogue code. Maybe I'm thinking about this the wrong way.

 -Hal

> 
> -Krzysztof
> 
> --
> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
> hosted by The Linux Foundation
>