similar to: How to best deal with undesirable Induction Variable Simplification?

I've noticed that there was an attempt to mitigate ExitValues problem in https://reviews.llvm.org/D12494 that went nowhere. Were there particular issues with that approach? -- Danila From: Philip Reames [mailto:listmail at philipreames.com] Sent: Saturday, August 10, 2019 02:05 To: Danila Malyutin <Danila.Malyutin at synopsys.com>; Finkel, Hal J. <hfinkel at anl.gov> Cc: llvm-dev

Thanks. I've rebased this patch on top of the recent LLVM (it was straightforward) and applied it in my fork. It seems to have solved one of the problems I was having. Would LLVM be interested if I submit the updated version for the review? -- Danila From: Philip Reames [mailto:listmail at philipreames.com] Sent: Tuesday, August 13, 2019 19:01 To: Danila Malyutin <Danila.Malyutin at

Hello, Recently I've come across two instances where Induction Variable Simplification lead to noticable performance regressions. In one case, the removal of extra IV lead to the inability to reschedule instructions in a tight loop to reduce stalls. In that case, there were enough registers to spare, so using extra register for extra induction variable was preferable since it reduced

There was this PR to use Jasmine: https://reviews.llvm.org/D20161 But I think it did not make it into tree. Kristof, any update on the issues you were encountering? We could move forward with that. I think we were pretty agnostic to which framework to use as long as it was not hard to install. JS Testing would be *really* good. I have debugged a lot of issues recently that ended up in the JS.

Hi, we at Arm have noticed that assembly can differ when compiling for AArch64 depending on whether debug information is generated or not. The issue is reproducible for the following small example compiled with `-O1` for `aarch64-arm-linux-gnu`: a() { b(a); for (;;) c("", b); } The reason for the difference is that AArch64 frame lowering emits CFI

> I don't understand why you want to factor out the information, > exactly. It seems like what you need is a function like: > > unsigned getMinLeadingZeros(const SCEV *); > > then, if you want to get the non-extended expression, you can just > apply an appropriate truncation. I assume, however, that I'm missing > something. The problem is not about how to codegen

Hello. We've started using LNT and found it very handy. However, we found that LNT web UI is missing some features to help our use-cases. We'd like to add them (and already started doing so) but it's hard to add them without breaking existing features/workflows because while LNT has some python CLI test coverage the dynamic Web part (mainly JS UI) is not really tested. So our question

Hi Folks, Let's keep this optimization alive. To summarize: several folks voiced general support, but with questions about why existing optimizations do not already catch this case. Deep dive by Wei Mi showed that the optimization is most likely not a clean-up of LSR sloppiness, but something new. Follow-up by myself confirmed that the redundancy eliminated the LoopExitValues pass exists in

Eli Friedman <eli.friedman <at> gmail.com> writes: > >> > I did not mention in the original email (and should have) that OSR needs > >> > -instcombine to be run after it for cleanup. Also -licm, -reassociate, -gvn > >> > and -sccp can be enabling optimizations for OSR. > >> > >> Hmm... perhaps that could be partially fixed

On Mon, Sep 21, 2015 at 11:13 AM, Wei Mi <wmi at google.com> wrote: > Maybe it can follow the "Delete dead loops" pass which is after > Induction Variable Simplification pass, so it will not affect existing > exitvalue rewriting optimization in Induction Variable Simplification > to find out and delete dead loops? > > Existing pass pipeline: >

Hi Steve it seems the general consensus is that the patch feels like a work-around for a problem with LSR (and possibly other loop transformations) that introduces redundant instructions. It is probably best to file a bug and a few of your test cases. Thanks Gerolf > On Sep 10, 2015, at 4:37 PM, Steve King via llvm-dev <llvm-dev at lists.llvm.org> wrote: > > On Thu, Sep 10, 2015

On 10/27/10 8:34 PM, Eli Friedman wrote: > On Wed, Oct 27, 2010 at 1:29 PM, Brian West<bnwest at rice.edu> wrote: >> Here is the patch for the new Operator Strength Reduction optimization >> pass that I have written. The bulk of the code is in >> >> lib/Transforms/Scalar/OperatorStrengthReduce.cpp >> >> The algorithm finds reduction opportunities in

----- Original Message ----- > From: "Bjarke Roune" <broune at google.com> > To: "Hal Finkel" <hfinkel at anl.gov> > Cc: llvmdev at cs.uiuc.edu, "Jingyue Wu" <jingyue at google.com> > Sent: Wednesday, July 1, 2015 2:27:59 PM > Subject: Re: [LLVMdev] Deriving undefined behavior from nsw/inbounds/poison for scalar evolution > >

Hi Adam, Indvar widening can sometimes be harmful for architectures (e.g. NVPTX and AMDGPU) where wider integer operations are more expensive ( https://llvm.org/bugs/show_bug.cgi?id=21148). For this reason, we disabled indvar widening in NVPTX in http://reviews.llvm.org/D6196. Hope it helps. Jingyue On Mon, Jun 29, 2015 at 11:59 AM Adam Nemet <anemet at apple.com> wrote: > > >

On Thu, Oct 28, 2010 at 9:38 AM, Brian West <bnwest at rice.edu> wrote: >> 3. LLVM already has a significant amount of infrastructure for loop >> passes; why does this pass have its own code for finding loops? > > I saw the loop infrastructure for CFG loops. This algorithm finds loops in > the data flow (more precisely: strongly-connected components in the >

On Fri, Sep 11, 2015 at 10:06 AM, Hal Finkel <hfinkel at anl.gov> wrote: > Also, if these redundant expressions involve induction variables, then that's something that the IndVarSimplify is already supposed to do, and if it is missing cases, then we should improve that pass (and, thus, folding what you've done into IndVarSimplify might be the right way to go). Hal, thanks for the

----- Original Message ----- > From: "Bjarke Roune" <broune at google.com> > To: "Jingyue Wu" <jingyue at google.com> > Cc: llvmdev at cs.uiuc.edu > Sent: Tuesday, June 30, 2015 8:16:13 PM > Subject: Re: [LLVMdev] Deriving undefined behavior from nsw/inbounds/poison for scalar evolution > > Hi Adam, > > Jingyue is right. We need to keep

Eli Friedman <eli.friedman <at> gmail.com> writes: > > Empirically the OSR optimization is compile-time faster than LSR. I have > > also noticed that OSR has more "analysis" requirements: Induction Variable > > User, Natural Loop Information, Canonicalize natural loops, and Scalar > > Evolution Analysis. Both OSR and LSR require the Dominator Tree

I am attempting to implement a minor loop strength reduction optimization for targets that support compare and jump fusion, specifically TTI::canMacroFuseCmp(). My approach might be wrong; however, I am soliciting the idea for feedback, so that I can implement this correctly. My plan is to add a Supplemental LSR formula to LoopStrengthReduce.cpp that optimizes the following case, but perhaps

*** Summary I'd like to propose (and implement) functionality in LLVM to determine when a poison value from an instruction is guaranteed to produce undefined behavior. I want to use that to improve handling of nsw, inbounds etc. flags in scalar evolution and LSR. I imagine that there would be other uses for it. I'd like feedback on this idea before I proceed with it. *** Details Poison