similar to: [LLVMdev] Chaitin-Briggs Register Allocation in LLVM

Hi, We noticed that LLVM has implemented register allocation using PBQP and Briggs as a heuristic for spilling. Is there a direct implementation of the Chaitin-Briggs register allocation algorithm? We intend to modify parts of this algorithm in order to implement a variant of it. It will save us a lot of time if it is already implemented, rather than writing the code from scratch. Thanks and

I seem to recall that LLVM had a Chaitin/Briggs register allocator, but looking at today's source, I only see a Linear Scan and some basic block allocators. Does anyone know if a Chaitin/Briggs allocator for LLVM exists and is available? Peter

Yes, I quite liked the things I've read about the PBQP allocator. Given what the hardware folks have to go through to get 1% improvements in scalar code, spending 20% (or whatever) compile time (under control of a flag) seems like nothing. And falling back on "average code" is a little disingenuous. People looking for performance don't care about average code; they care about

Hi, Using Chaitin's approach, removing a copy via coalescing could expose more opportunities for coalescing. So he would iteratively rebuild the interference graph and check for more opportunities. Chaitin was also careful to make sure that the source and destination of a copy didn't interfere unnecessarily (because of the copy alone); that is, his approach to interference was very

Hello, I want learn more about register allocation and do some analysis for a current research project. After reading some papers (eg. Chaitin, Briggs) I think its time to get my hands dirty :). First I plan to (re)implement some of the classic approaches to get familiar with the framework. At the beginning the following questions came up: - Is there some documentation about register allocation

On Saturday 01 May 2010 08:34:50 Josef Eisl wrote: > Hello, > > I want learn more about register allocation and do some analysis for a > current research project. After reading some papers (eg. Chaitin, > Briggs) I think its time to get my hands dirty :). Welcome! > First I plan to (re)implement some of the classic approaches to get > familiar with the framework. Before

> On Sep 11, 2018, at 11:42 AM, Quentin Colombet <quentin.colombet at gmail.com> wrote: > > Le mar. 11 sept. 2018 à 11:23, Preston Briggs > <preston.briggs at gmail.com> a écrit : >> >> Yes, I quite liked the things I've read about the PBQP allocator. >> >> Given what the hardware folks have to go through to get 1% improvements in scalar code,

> On Sep 10, 2018, at 5:25 PM, Matthias Braun <mbraun at apple.com> wrote: > > > >> On Sep 10, 2018, at 5:11 PM, Preston Briggs <preston.briggs at gmail.com <mailto:preston.briggs at gmail.com>> wrote: >> >> The phi instruction is irrelevant; just the way I think about things. >> The question is if the allocator believes that t0 and t2

The phi instruction is irrelevant; just the way I think about things. The question is if the allocator believes that t0 and t2 interfere. Perhaps the coalescing example was too simple. In the general case, we can't coalesce without a notion of interference. My worry is that looking at interference by ranges of instruction numbers leads to inaccuracies when a range is introduced by a copy.

> The underlying liveness datastructure is a list of ranges where each vreg is alive > (ranges in terms of instructions numbered). I remember a couple of later linear scan > papers describing the same thing (Traub et.al. being the first if I remember correctly). > That should be as accurate as you can get in terms of liveness information. It depends on the details. For example, given

Hi Matthias, Thanks for your hint! It is just for learning and practicing for me, just like migrate DragonEgg http://lists.llvm.org/pipermail/llvm-dev/2017-September/117201.html the motivating is for learning from GCC and LLVM developers. 在 2017年12月19日 10:07, Matthias Braun 写道: > > >> On Dec 18, 2017, at 9:52 AM, Leslie Zhai via llvm-dev >> <llvm-dev at lists.llvm.org

Hi Jakob, Thanks for a very interesting description of the new register allocation algorithm in LLVM!!! Could you elaborate a bit on the following topics: 1) Do you have any plans to publish something more formal and detailed about this algorithm, e.g. a paper or something similar?  It would be nice to better understand how this algorithm relates to well-known algorithms described in the

Hi Leslie, I suggest adding these 3 papers to your reading list. Register allocation for programs in SSA-form Sebastian Hack, Daniel Grund, and Gerhard Goos http://www.rw.cdl.uni-saarland.de/~grund/papers/cc06-ra_ssa.pdf Simple and Efficient Construction of Static Single Assignment Form Matthias Braun , Sebastian Buchwald , Sebastian Hack , Roland Leißa , Christoph Mallon , and Andreas

David Greene wrote: > On Saturday 01 May 2010 08:34:50 Josef Eisl wrote: >> Hello, >> >> I want learn more about register allocation and do some analysis for a >> current research project. After reading some papers (eg. Chaitin, >> Briggs) I think its time to get my hands dirty :). > > Welcome! > >> First I plan to (re)implement some of the classic

On Sep 26, 2011, at 4:22 AM, Leo Romanoff wrote: > Hi Jakob, > > Thanks for a very interesting description of the new register allocation algorithm in LLVM!!! > > Could you elaborate a bit on the following topics: > > 1) Do you have any plans to publish something more formal and detailed about this algorithm, e.g. a paper or something similar? It would be nice to better

I just uploaded a blog post outlining the new register allocation algorithm in LLVM 3.0. http://blog.llvm.org/2011/09/greedy-register-allocation-in-llvm-30.html Please direct comments here. /jakob

How precise is the interference checking (to my mind, a great weakness of linear scan)? Is there way to do coalescing (the great strength of coloring)? I ask these questions because we (guys I work with) see loops where there's a little register juggling that seems unnecessary. Is there a paper that describes what y'all do? Thanks, Preston On Mon, Sep 10, 2018 at 9:57 AM, Matthias

Last Friday, Gregory Chaitin (http://www.umcs.maine.edu/~chaitin/lm.html) mentioned that there can be no proof that a given code is the shortest for a problem, even within a language. Still, the script below, a replacement of the "TDT", one of the most frequently used tests in genetics (http://mustat.rockefeller.edu under "downloads") may get close. It contains a few

Hi all, Just wanted to announce that I've implemented a preliminary version of a Chaitin-Briggs graph coloring register allocator for the LLVM x86 back-end. Right now, as it stands, the allocator works correctly for the benchmarks that I tested it on (from the LLVM test suite and some of the SPEC benchmarks). It performs better than the local register allocator in terms of spills and

Preston, thanks for the explanation and patch. Now it's printing the direction and distance values. On Tue, Nov 13, 2012 at 12:22 PM, Preston Briggs <preston.briggs at gmail.com>wrote: > Erkan, you're right. Sorry about that. > Attached is the most recent version. > > Preston > > > > Hi Preston, >> I am trying to use DA as well. I used your example