similar to: [LLVMdev] enable globalsmodref-aa by default

Before the fix, the compiler may simply return 'noalias' for cases it can not really prove to be noalias, but actually correct by luck (or even wrong noalias, but does not result in miscompile). It would be useful to find out the set of missed noalias queries from GlobalModRef with your benchmark and examine if there is some improvement can be done. David On Fri, Jul 17, 2015 at 6:32

Hi Xin, Thank you for your reply! I have tried the 3 alias analyses you have mentioned on LLVM 3.5: 1) $ opt -globalsmodref-aa -aa-eval < xxx.bc > /dev/null (May-alias response 100%) 2) $ opt -tbaa -aa-eval < xxx.bc > /dev/null (May-alias response 100%) 3) $ opt -cfl-aa -aa-eval < xxx.bc> /dev/null (Unknown command line argument '-cfl-aa') It seems that they are not

Hi there, I am doing: opt -print-memdeps ./test.bc -analyze -globalsmodref-aa by adding globalsmodref-aa, I am hoping that globalsmodref alias analysis will be used. However, it does not turn out to be so. I found this out by adding some "errs() << " into the source code for that alias analysis. So my question is what should I do to let memory dependency analysis use

Hi all, I'm implementing an intra-procedural analysis. For correctness, during the analysis of each function I need to know which global variables may be modified by other functions in order to avoid wrong assumptions about those variables. I looked at lib/Analysis/IPA/GlobalsModRef.cpp and it seems that it does what I want. My problem is that I don't know how to use it ;-( I wrote a

Hi Jorge, > I'm implementing an intra-procedural analysis. For correctness, during > the analysis of each function I need to know which global variables > may be modified by other functions in order to avoid wrong assumptions > about those variables. > > I looked at lib/Analysis/IPA/GlobalsModRef.cpp and it seems that it > does what I want. My problem is that I don't

Hi I have this program in which fooBuf can only take on NULL or the address of local_fooBuf, and fooBuf and local_fooBuf have scope of the foo function. Therefore there is no way for the fooPtr argument to alias with fooBuf. However, LLVM basicaa and globalsmodref-aa say the 2 pointers may alias. I am thinking whether i should implement a limited form of point-to alias on the fooBuf pointer in

Hey, thanks for benchmarking. How stable is the 2% regression? Michael ran some benchmarks with GlobalsModRef completely disabled and the only differences were in the noise. This was a complete spec2k6 run along with some others. Based on the number of benchmarks run there, I'm going to go ahead and submit these patches, but if you can clarify the impact here, we can look at potentially some

>> 2) is just for being pedantic :-) >> >> One might otherwise argue in this snippet, x apparently does not have >> its addr taken, >> however, it's illegal to say that "x" and "*p" don't alias. > Wait, really? I thought that "volatile static int x" just meant that the value of x was volatile; not that 'x' might

----- Original Message ----- > From: "Chris Lattner" <clattner at apple.com> > To: "Chandler Carruth" <chandlerc at gmail.com> > Cc: "LLVM Developers Mailing List" <llvmdev at cs.uiuc.edu>, "Hal Finkel" <hfinkel at anl.gov>, "Justin Bogner" > <mail at justinbogner.com>, "Duncan Exon Smith"

Dear all, I was wondering if there are some reliable alias analyses build on top of LLVM other than basicaa. Thank you! Zhiyuan -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20150407/db07dba3/attachment.html>

Ok folks, I wrote up the general high-level thoughts I have about stateful AA in a separate thread. But we need to sort out the completely and horribly broken aspects of GlobalsModRef today, and the practical steps forward. This email is totally about the practical stuff. Now, as to why I emailed this group of people and with this subject, the only pass pipeline that includes GlobalsModRef, is

On Mon, Jul 13, 2015 at 10:21 PM Chris Lattner <clattner at apple.com> wrote: > > > On Jul 13, 2015, at 8:19 PM, Chandler Carruth <chandlerc at gmail.com> > wrote: > > > > Ok folks, > > > > I wrote up the general high-level thoughts I have about stateful AA in a > separate thread. But we need to sort out the completely and horribly broken >

Greetings folks! I would like to enable globalsmodref-aa in the non-LTO pass pipeline so that it gets tested more and there are fewer differences between the two. For all of my benchmarks, this is performance neutral, but I'd appreciate others benchmarking this combination to see if they see any benefits or regressions. You can demo this mode easily: -mllvm -enable-non-lto-gmr Please let me

Can you say what Benchmark or give a test case so we understand the nature of the regression? As Gerolf said, that will be important to understand what is best to do. On Fri, Jul 17, 2015, 06:43 Evgeny Astigeevich <Evgeny.Astigeevich at arm.com> wrote: > Yes, the regression is stable. I double checked this. A full benchmark > run consists of at least 10 sub-runs to validate the

On Fri, Jul 17, 2015 at 9:13 AM Evgeny Astigeevich < evgeny.astigeevich at arm.com> wrote: > It’s Dhrystone. > Dhrystone has historically not been a good indicator of real-world performance fluctuations, especially at this small of a shift. I'd like to see if we see any fluctuation on larger and more realistic application benchmarks. One advantage of the flag being set is that we

Hi Chandler, I would like to run some benchmarks on ARM hardware and to look at impact of your patches on LTO. Kind regards, Evgeny Astigeevich From: llvmdev-bounces at cs.uiuc.edu [mailto:llvmdev-bounces at cs.uiuc.edu] On Behalf Of Chandler Carruth Sent: 15 July 2015 10:45 To: Chandler Carruth; Gerolf Hoflehner Cc: LLVM Developers Mailing List Subject: Re: [LLVMdev] GlobalsModRef

On Tue, Jan 3, 2012 at 4:55 PM, Chris Lattner <clattner at apple.com> wrote: > On Jan 3, 2012, at 1:53 PM, Jianzhou Zhao wrote: >> I see. I asked the question because LLVM provides several alias >> analysis, and I was wondering how to decide which one should be used >> for compiling most programs. >> >> I think the basicaa is the default one, but by looking

On Oct 29, 2013, at 7:11 PM, Shuxin Yang <shuxin.llvm at gmail.com> wrote: >> Also, as a general note, I don't see why any of this should be LTO-specific. For variables with local (internal) linkage, we can do the analysis on a per-module basis, and I don't understand why we currently don't. >> >> Thanks again, >> Hal >> >> > You can

Based on function names and structures, this is some version of GCC :) Any way you can post the entire .ll file? Because it's globalsmodref, it's hard to debug without the other functions, since it goes over all the functions to determine address takenness, etc :) On Tue, Jul 21, 2015 at 3:23 PM, Michael Zolotukhin <mzolotukhin at apple.com> wrote: > Hi Chandler, > > We

Replying here, but several of the questions raised boil down to "couldn't you make the usage of GetUnderlyingObject conservatively correct?". I'll try and address that. I think this *is* the right approach, but I think it is very hard to do without effectively disabling this part of GlobalsModRef. That is, the easy ways are likely to fire very frequently IMO. The core idea is