search for: interferences

...s Z AND there's an interception between the ranges of X and ranges of Y", that's something like "X overlaps Y, which are the same type". This deffinition differs from the definition I've found reading the source code. In the class LiveRegMatrix, which is queried to check interferences you ask something "does virtual register X interfere in physical register Y?". But I realized the answer is yes only if register Y has been already assigned to another virtual register. I confess I couldn't understand why it was implemented in that way. That means I must first assign...

...re's an interception between the ranges of X and ranges of Y", that's something like "X overlaps Y, which are the same type". > > This deffinition differs from the definition I've found reading the source code. In the class LiveRegMatrix, which is queried to check interferences you ask something "does virtual register X interfere in physical register Y?". But I realized the answer is yes only if register Y has been already assigned to another virtual register. > > I confess I couldn't understand why it was implemented in that way. That means I must fi...

Good Night. I'm implementing a Interference Graph in the Register Allocation pass. I'm building this graph BEFORE any assignment of a virtual register to physical register. But I have a doubt about how to check the interference between two Live Intervals (i.e. They live at same point), should I use: L1->overlaps(L2) Where L1 and L2 are two different Live Intervals. Or should I use:

Ok, just to clarify, RegUnits, as far I understand, are Physical registers or alias to Physical registers. They exist because some instructions use physical registers directly rather than virtual register. It's right? And why this RegUnits should be present in the Interference Graph? I thought were only the Live Intervals would be the nodes of the graph. Sorry about the trouble to

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

> 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

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

Toward a better register allocator, I'm attempting to understand the dataflow information available to the allocator. What's the difference between LiveInterval information and LiveVariable information? If a LiveInterval is based on a linear ordering of the machine instructions, isn't it rather conservative in nature? Let's say I have a typical diamond CFG: A

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, We have found that exist a huge degradation in performance when doing I/O to a disk images contained in single files from a paravirtualized domain and from an HVM at the same time. The problem was found in a Xen box with Fedora 8 x86_64 binaries installed (Xen 3.1.0 + dom0 Linux 2.6.21). The test hardware was a rack mounted server with two 2.66 Ghz Xeon X5355 (4 cores each one, 128 Kb L1

On Jul 17, 2007, at 8:40 AM, David Greene wrote: > On Monday 16 July 2007 18:19, Evan Cheng wrote: > >> Sorry I should have replied earlier. I really don't like this dual >> interface approach. To me, this muddles things without offering any >> real useful new functionalities. > > Ok. See below for the rationale. > >> IMHO, if a register coalescer is

Hi, I worked in llvm to get some information from live variable analysis. If the live range of one variable interferes with another, we could record the related two variables into a pair. For example, with a function with local variables 'a', 'b', 'c', 'x' and 'y', the pair set { (a, b), (b,c), (x,y)} indicates that 'a' interferes with 'b',

Hi, I have a frontend that could insert many calls to an external threading library, my problem is that would interfere with optimizations, particularly the inliner. Is there some way to do this ? I've considered leaving textual markers in function names, is that a legitimate solution ? James -------------- next part -------------- An HTML attachment was scrubbed... URL:

On 20/09/05, Chris Lattner <sabre at nondot.org> wrote: > > because LiveVariables do not provide an interface to iterate through > > all viritual registers. > > Ok, you could add a method to LiveVariables that returns > VirtRegInfo.size(). The virtual registers are defined by the range: > [MRegisterInfo::FirstVirtualRegister, >

On Tuesday 17 July 2007 13:06, Evan Cheng wrote: > > These two requirements led to the abstract RegisterCoalescer > > interface in the patch. This is the interface that register > > allocators > > know about. Likewise, coalescers need an abstract interface to > > register allocators to ask questions and do other things. > > If the two modules need to share

On 4/3/07, David Greene <greened at obbligato.org> wrote: > > Toward a better register allocator, I'm attempting to understand > the dataflow information available to the allocator. > > What's the difference between LiveInterval information and LiveVariable > information? If a LiveInterval is based on a linear ordering of > the machine instructions, isn't it

Hi Kameshwar, You're best off sending emails such as this to the LLVM developers mailing list (llvmdev at cs.uiuc.edu). You'll reach a much wider audience. The PBQPRegAlloc::buildInterferenceMatrix method constructs a PBQP cost matrix representing a single interference constraint, which doesn't sound like what you want. It is only used by the PBQP allocator (-regalloc=pbqp), whereas

LiveVariables gives you something like liveness analysis: where each variable is alive, that is, across each basic blocks, where it is defined, and where it is killed. LiveIntervals gives you a linear representation of the variables as a set of intervals. Yes, it handle holes in the live ranges. There is a very nice description of these analysis and related data structures here:

On Tue, 20 Sep 2005, Tzu-Chien Chiu wrote: > On 20/09/05, Chris Lattner <sabre at nondot.org> wrote: >>> because LiveVariables do not provide an interface to iterate through >>> all viritual registers. >> >> Ok, you could add a method to LiveVariables that returns >> VirtRegInfo.size(). The virtual registers are defined by the range: >>