[LLVMdev] Heads up: Pass Manager changes will be starting shortly

Andrea_DiBiagio at sn.scee.net Andrea_DiBiagio at sn.scee.net
Mon Sep 16 04:33:00 PDT 2013

I have a question about the design of the new pass manager.
In the RFC on "codifying the optimization levels in clang and LLVM" ( 
http://lists.cs.uiuc.edu/pipermail/llvmdev/2013-January/058112.html ) the 
idea was expressed of having function attributes to allow specific 
functions to override the command line optimization level. If at some 
point we decide to go in that direction and we introduce function 
attributes for the remaining optimization levels (I am currently working 
on the 'optnone' attribute which ideally could match optlevel -O0) how 
would this affect the designing of the new pass manager?
I was wondering if you plan to design the new pass manager to 
simplify/help achieving this goal?
Do you plan to address the problems raised only by "Pass Manager Redux" (
or do you also plan to investigate the optimization levels idea which I 
expressed here?

Andrea Di Biagio

> From: Sean Silva <silvas at purdue.edu>
> To: Chandler Carruth <chandlerc at google.com>, 
> Cc: Reed Kotler <rkotler at mips.com>, LLVM Developers Mailing List 
> <llvmdev at cs.uiuc.edu>, Andrea_DiBiagio at sn.scee.net
> Date: 16/09/2013 01:15
> Subject: Re: [LLVMdev] Heads up: Pass Manager changes will be starting 
> On Sun, Sep 15, 2013 at 8:08 PM, Sean Silva <silvas at purdue.edu> wrote:
> On Sat, Sep 14, 2013 at 7:05 PM, Chandler Carruth <chandlerc at google.com
> > wrote:
> On Sat, Sep 14, 2013 at 3:57 PM, Reed Kotler <rkotler at mips.com> wrote:
> Hi Chandler,
> What changes are you planning to make?
> Are you going to submit a proposal and RFC?
> There have been several RFCs...
> What's your specific question?
> I'm planning to essentially try to build a new pass management layer
> that doesn't suffer from the problems the existing one does. I could
> describe every interface I plan in prose and email it out, but I'm 
> not sure that's really the most effective way to do it. My plan has 
> been to work on implementing the new system in-tree, and let folks 
> code review it and pick it apart as usual. When folks are happy with
> it, and it works, then we can look at switching over.
> I think it would be nice just to centralize the results of all 
> discussions thus far in a google doc or whatever.
> I don't recall ever seeing in one place a listing of the primary 
> issues that the rewrite is meant to address. I've definitely seen 
> various discussions here and there from time to time, but nothing 
> that a person could look at and get a big picture view of what's 
> happening and why.
> -- Sean Silva 
> Do'h, just saw you mention downthread of the "Pass Manager Redux" 
> you posted like a year ago ("redux" was apparently the word that was
> missing from all my mail searches). (It's been a year, can you blame
> me for not remembering? ;) )
> -- Sean Silva

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