[LLVMdev] Question regarding basic-block placement optimization

Jakob Stoklund Olesen stoklund at 2pi.dk
Thu Oct 20 10:53:34 PDT 2011

On Oct 20, 2011, at 9:56 AM, Chandler Carruth wrote:

> A new patch is attached that is *much* less of a rough draft. Sorry for any confusion due to the early state of the patch.

Thanks, Chandler. This is great stuff.

> Still, I never intended this to be on-by-default at first. This is a starting point, that I hope can be improved into something that is on-by-default eventually, but I'll be the first to say it's almost certainly not ready for that just yet.

I would like to see this go in ASAP under a flag. I prefer to see development as commits rather than a series of updated patches.

Could you rename it to MachineBlockPlacement.cpp first, though? That makes it clear it's a CodeGen pass, and the BlockPlacement2 name is icky.

> I'm more hopeful that we can delete the existing block placement pass, and direct anyone interested in profile file guided stuff to write a simple pass to load profiles into metadata. I suspect this pass is already superior to that one.

I also see it as a replacement for CodePlacementOpt.cpp, so I think your flag should run your pass instead of CodePlacementOpt rather than before or after it.

You should simply clone the loop alignment stuff, it's pretty trivial.


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