similar to: [LLVMdev] Alias Analysis accuracy

Here is the result of running mem2reg then basicaa, it is even worse: (%a should be alias to %0, and partial alias to %3) opt -mem2reg -basicaa -aa-eval -print-all-alias-modref-info < foo.s > /dev/null Function: foo: 6 pointers, 0 call sites NoAlias: i32* %a, i32* %b NoAlias: i32* %a, i32* %c NoAlias: i32* %b, i32* %c PartialAlias: i32* %1, i32* %a NoAlias:

On Fri, Sep 21, 2012 at 3:08 PM, Welson Sun <welson.sun at gmail.com> wrote: > OK, with the restrict type qualifier, it is a little bit better: > > The IR's function signature becomes: > define void @foo(i32* noalias %a, i32* noalias %b, i32* noalias %c) nounwind > { > > Now the AA result: > Function: foo: 13 pointers, 0 call sites > NoAlias: i32* %a,

OK, with the restrict type qualifier, it is a little bit better: The IR's function signature becomes: define void @foo(i32* noalias %a, i32* noalias %b, i32* noalias %c) nounwind { Now the AA result: Function: foo: 13 pointers, 0 call sites NoAlias: i32* %a, i32* %b NoAlias: i32* %a, i32* %c NoAlias: i32* %b, i32* %c NoAlias: i32* %a, i32** %a_addr NoAlias:

Can you give an example? And is this limited to C (not C++) only? On Fri, Sep 21, 2012 at 2:52 PM, Liu, Yaxun (Sam) <Yaxun.Liu at amd.com> wrote: > I think you may add restrict type qualifier.**** > > ** ** > > Sam**** > > ** ** > > *From:* llvmdev-bounces at cs.uiuc.edu [mailto:llvmdev-bounces at cs.uiuc.edu] *On > Behalf Of *Welson Sun > *Sent:* Friday,

Great! That makes sense! Thank you! On Fri, Sep 21, 2012 at 3:43 PM, Arnold Schwaighofer < arnold.schwaighofer at gmail.com> wrote: > You see the result for running basicaa after mem2reg. > > The IR after mem2reg will look like (you can look at it by doing > -mem2reg -basicaa -aa-eval -print-all-alias-modref-info < test.ll > -print-after-all) > > define void

Yeah. Is there a way to specify noalias between these arguments? On Fri, Sep 21, 2012 at 2:46 PM, Krzysztof Parzyszek < kparzysz at codeaurora.org> wrote: > On 9/21/2012 4:35 PM, Welson Sun wrote: > >> Dear LLVM, >> >> I would like to understand how to improve the LLVM alias analysis >> accuracy. I am currently using llvmgcc 2.9 and llvm 3.0. Here is the C

> Fixing that still gives a wrong result, i haven't started to track down what *else* is going on here. Running with the attached diff + a modified buildGraphFrom to handle the constexpr GEPs, we seem to flag everything in test2.ll (conservatively) correctly. Is `store` the only place we can expect to see these constexpr analogs, or is just about anywhere fair game? George On Fri, Jan

I think you may add restrict type qualifier. Sam From: llvmdev-bounces at cs.uiuc.edu [mailto:llvmdev-bounces at cs.uiuc.edu] On Behalf Of Welson Sun Sent: Friday, September 21, 2012 5:50 PM To: Krzysztof Parzyszek Cc: llvmdev at cs.uiuc.edu Subject: Re: [LLVMdev] Alias Analysis accuracy Yeah. Is there a way to specify noalias between these arguments? On Fri, Sep 21, 2012 at 2:46 PM, Krzysztof

Without the patch is also returns the wrong answer for all of these, it just doesn't cause LICM to promote because it returns PartialAlias (which is still wrong). We return may-alias instead, and now suddenly it's happy to promote them. The broken noalias results exist both before and after my patch: ===== Alias Analysis Evaluator Report ===== 521 Total Alias Queries Performed

Hi, We've seen a similar case recently, where BasicAA returns PartialAlias for the access of two different fields of a structure. We noticed this since Lint complained about it when checking for aliasing beteen "noalias" attributed parameters: opt -S -lint ./alias.ll gave Unusual: noalias argument aliases another argument on the (silly) function: %rec7 = type { i16, i16, i16

No, i mean the actual store instruction looks like "store i16 %conv22, i16* getelementptr inbounds ([16 x i16]* @pA, i64 0, i64 12), align 2, !tbaa !1" Not that the pointer operand comes from a GEP, but it is a constantexpr, whose opcode is GEP. It sucks that there is such a complex thing to be handled as a store operand directly , but such is life ... CFL-AA *should* treat this

Updated testcases to have MayAlias/note issues as FIXME. On Tue Jan 20 2015 at 3:54:10 PM Hal Finkel <hfinkel at anl.gov> wrote: > ----- Original Message ----- > > From: "Daniel Berlin" <dberlin at dberlin.org> > > To: "Hal Finkel" <hfinkel at anl.gov> > > Cc: "Jiangning Liu" <Jiangning.Liu at arm.com>, "George

On Wed Jan 21 2015 at 12:30:50 PM Hal Finkel <hfinkel at anl.gov> wrote: > ----- Original Message ----- > > From: "Daniel Berlin" <dberlin at dberlin.org> > > To: "Hal Finkel" <hfinkel at anl.gov> > > Cc: "Jiangning Liu" <Jiangning.Liu at arm.com>, "George Burgess IV" < > george.burgess.iv at gmail.com>,

> Should we be added an edge from the inttoptr to all other pointer values? Is there a better way? We can add a special "Unknown" StratifiedAttr and query it before anything else, i.e: // in CFLAliasAnalysis::query, as the first potential return if (AttrsA[AttrUnknown] || AttrsB[AttrUnknown]) return MayAlias; The only *potential* issue with this approach would be that in the

----- Original Message ----- > From: "Daniel Berlin" <dberlin at dberlin.org> > To: "Hal Finkel" <hfinkel at anl.gov> > Cc: "Jiangning Liu" <Jiangning.Liu at arm.com>, "George Burgess IV" <george.burgess.iv at gmail.com>, "LLVM Developers > Mailing List" <llvmdev at cs.uiuc.edu>, "Nick Lewycky"

I'm not exactly thrilled about the size of this diff -- I'll happily break it up into more manageable bits later today, because some of it is test fixes, another bit is a minor bug fix, etc. Important bit (WRT ConstantExpr): moved the loop body from buildGraphFrom into a new function. The body has a few tweaks to call constexprToEdges on all ConstantExprs that we encounter.

Works for me On Thu, Jan 22, 2015 at 8:27 PM, Daniel Berlin <dberlin at dberlin.org> wrote: > We should use graph edges, so we can do something better at set build time > :) > > > On Thu Jan 22 2015 at 5:20:46 PM George Burgess IV < > george.burgess.iv at gmail.com> wrote: > >> > Should we be added an edge from the inttoptr to all other pointer >>

Hello all, I observed that BasicAA alias query returns PartialAlias between different fields of a structure. Following is the test program and -print–all-alias-modref-info output: --- ; test.ll target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128" target triple = "x86_64-unknown-linux-gnu" %"type" = type { [10 x i32], i64 } define void

Yes. I've attached an updated patch that does the following: 1. Fixes the partialalias of globals/arguments 2. Enables partialalias for cases where nothing has been unified to a global/argument 3. Fixes that select was unifying the condition to the other pieces (the condition does not need to be processed :P). This was causing unnecessary aliasing. 4. Adds a regression test to

So, I can make all these testcases work, but it's a little tricky (it involves tracking some things, like GEP byte range, and then checking bases and using getObjectSize, much like BasicAA does). Because i really don't want to put that much "not well tested" code in a bugfix, and honestly, i'm not sure we will catch any cases here that BasicAA does not, i've attached a