[PATCH] LocalStackSlotAllocation improvements

[Hal Finkel]

Jim okayed this off-list. r180799.

 -Hal

----- Original Message -----
> From: "Hal Finkel" <hfinkel at anl.gov>
> To: "Jim Grosbach" <grosbach at apple.com>
> Cc: "Commit Messages and Patches for LLVM" <llvm-commits at cs.uiuc.edu>
> Sent: Tuesday, April 16, 2013 3:39:40 PM
> Subject: Re: [PATCH] LocalStackSlotAllocation improvements
> 
> Ping.
> 
>  -Hal
> 
> ----- Original Message -----
> > From: "Hal Finkel" <hfinkel at anl.gov>
> > To: "Jim Grosbach" <grosbach at apple.com>
> > Cc: "Commit Messages and Patches for LLVM"
> > <llvm-commits at cs.uiuc.edu>
> > Sent: Monday, April 8, 2013 6:33:35 PM
> > Subject: [PATCH] LocalStackSlotAllocation improvements
> > 
> > Jim, et al.,
> > 
> > Please review the attached patch that improves
> > LocalStackSlotAllocation. It does a few things:
> > 
> >  - Taking advantage of the fact that the virtual base registers are
> >  allocated in order of the local frame offsets, remove the
> >  quadratic
> >  register-searching behavior. Because of the ordering, we only need
> >  to check the last virtual base register created.
> > 
> >  - Store the frame index in the FrameRef structure, and get the
> >  frame
> >  index and the local offset from this structure at the top of the
> >  loop iteration. This allows us to de-nest the loops in
> >  insertFrameReferenceRegisters (and I think makes the code
> >  cleaner).
> >  I also moved the needsFrameBaseReg check into the first loop over
> >  instructions so that we don't bother pushing FrameRefs for
> >  instructions that don't want a virtual base register anyway.
> > 
> >  - Avoids the creation of single-use virtual base registers. These
> >  are currently not useful because, in general, they end up
> >  replacing
> >  what would be one r+r instruction with an add and a r+i
> >  instruction.
> > 
> > Thanks again,
> > Hal
> > 
> > P.S. I'll commit some tests to cover the single-use behavior when I
> > enable this on PPC.
> > 
> > --
> > Hal Finkel
> > Postdoctoral Appointee
> > Leadership Computing Facility
> > Argonne National Laboratory
> > 
> > _______________________________________________
> > llvm-commits mailing list
> > llvm-commits at cs.uiuc.edu
> > http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
> > 
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