search for: scevunknowns

Hi, We come across a ScalarEvolution (SE) problem the other day. It seems to be a fundamental design problem. I don't think I have a clean and cheap fix to this problem. I talked with Andy in the phone yesterday, he told me it is a known fundamental problem. But I don't see any discussion on this problem on the list, so I post the problem here, soliciting your insightful comment.

On Fri, 2011-11-11 at 23:55 +0100, Tobias Grosser wrote: > On 11/11/2011 11:36 PM, Hal Finkel wrote: > > On Thu, 2011-11-10 at 23:07 +0100, Tobias Grosser wrote: > >> On 11/08/2011 11:29 PM, Hal Finkel wrote: > >> Talking about this I looked again into ScalarEvolution. > >> > >> To analyze a load, you would do: > >> > >> LoadInst *Load

The Problem? Nowaday, SCEV called "Scalar Evolution" does only evolate instructions that has predictable operand, Constant-Based operand. such as that can evolute as a constant. otherwise we couldn't evolate it as SCEV node, evolated as SCEVUnknown. important thing that we remember is, we do not use SCEV only for Loop Deletion, which that doesn't really needed on nature loops

On 11/12/2011 12:11 AM, Hal Finkel wrote: > On Fri, 2011-11-11 at 23:55 +0100, Tobias Grosser wrote: >> On 11/11/2011 11:36 PM, Hal Finkel wrote: >>> On Thu, 2011-11-10 at 23:07 +0100, Tobias Grosser wrote: >>>> On 11/08/2011 11:29 PM, Hal Finkel wrote: Talking about this I >>>> looked again into ScalarEvolution. >>>> >>>> To

On Sun, 7 Oct 2012 18:53:59 -0700 Preston Briggs <preston.briggs at gmail.com> wrote: > I'd like a value, call it Bottom, such that > > SE->getAddExpr(Bottom, X) => Bottom > SE->getMulExpr(Bottom, X,) => Bottom > isKnownPredicate(any, Bottom, X) => false > etc. > > > I can write code to make NULL work like I want, but it would be > simpler

I'd like a value, call it Bottom, such that SE->getAddExpr(Bottom, X) => Bottom SE->getMulExpr(Bottom, X,) => Bottom isKnownPredicate(any, Bottom, X) => false etc. I can write code to make NULL work like I want, but it would be simpler if something was already defined. I'm wondering about SCEV::Unknown. The documentation suggests I could perhaps use it for a

Tobias Grosser wrote: > You create a map from the old_loop to a symbolic expression. What type would > this symbolic expression have? Would it be a SCEVExpr? evaluateAtIteration takes a scev, so apply will take a scev, or a map (loop->scev). You can always build a ScevUnknown from an SSA name and use that in the apply. > At the moment, we calculate at the beginning of each >

On Thu, 2011-11-10 at 23:07 +0100, Tobias Grosser wrote: > On 11/08/2011 11:29 PM, Hal Finkel wrote: > > On Tue, 2011-11-08 at 20:24 +0100, Tobias Grosser wrote: > >> On 11/08/2011 03:36 PM, Hal Finkel wrote: > >>> On Tue, 2011-11-08 at 12:12 +0100, Tobias Grosser wrote: > >>>> On 11/08/2011 11:45 AM, Hal Finkel wrote: > > [A lot of performance

On 11/11/2011 11:36 PM, Hal Finkel wrote: > On Thu, 2011-11-10 at 23:07 +0100, Tobias Grosser wrote: >> On 11/08/2011 11:29 PM, Hal Finkel wrote: >> Talking about this I looked again into ScalarEvolution. >> >> To analyze a load, you would do: >> >> LoadInst *Load = ... >> Value *Pointer = Load->getPointer(); >> const SCEV *PointerSCEV =

The SCEV framework sorts operands of commutative SCEVs by their getSCEVType() value, and then does an ad-hoc sort to group repeated operands, but it does not do a full sort. In some test cases I'm looking at right now, this causes it to miss opportunities to reuse SCEV objects, as in cases like this: ( %i + %r54 + %r59) ( %r54 + %r59 + %i) As a result, passes like LoopStrengthReduce

On 11/08/2011 11:29 PM, Hal Finkel wrote: > On Tue, 2011-11-08 at 20:24 +0100, Tobias Grosser wrote: >> On 11/08/2011 03:36 PM, Hal Finkel wrote: >>> On Tue, 2011-11-08 at 12:12 +0100, Tobias Grosser wrote: >>>> On 11/08/2011 11:45 AM, Hal Finkel wrote: [A lot of performance results skipped] OK. As expected part of the speedup is because of unrolling, however it

Hi Preston, I was wondering ... "Bottom" is a bit overloaded as far as terms go. Would SCEVNaN be a better name for this beast? Sameer. > -----Original Message----- > From: llvmdev-bounces at cs.uiuc.edu [mailto:llvmdev-bounces at cs.uiuc.edu] On > Behalf Of Sameer Sahasrabuddhe > Sent: Monday, October 08, 2012 9:16 AM > To: preston.briggs at gmail.com > Cc: LLVM

...extra code that needs to be added, but why is it what it is? After extra formulas are generated, some of them can contain constants that were not in the code before and thus may require an instruction to put them into a register, yet for constants the SetupCost will be 0. On a similar note, are SCEVUnknowns presumed to already have a register? 3. isLegalAddressingMode There are many addressing modes that are legal on Hexagon, yet given a choice, some are preferable to others. LSR treats all of them as equivalent as long as a formula can be folded completely into it. Has anyone thought about makin...

2011/11/21 Tobias Grosser <tobias at grosser.es>: > On 11/20/2011 04:36 PM, Marcello Maggioni wrote: >> >> Sorry for the noobish question, but what kind of subscripts generate a >> SCEVCouldNotCompute  from the SCEV engine? >> I tried for a while but I wasn't able to trigger that > > Hi Marcello, > > the SCEV returns SCEVCouldNotCompute in case it

On 11/14/2011 01:24 AM, Marcello Maggioni wrote: > Hi Tobias. > > I worked on enabling Polly accepting non affine memory accesses and I > produced a patch. Great. > I saw that there were a lot of updates in Polly recently, so I had to > redo a lot of the work I did and that slowed me quite a bit. Ups, sorry! However, I believe without these changes detecting non-affine memory

On 11/18/2011 01:34 PM, Marcello Maggioni wrote: > Ok , this is what I believe is the final patch that adds the > non-affine accept functionality to Polly, this should have no issues. > > I added three tests, two in ScopInfo (two simple tests, one expected > fail and one success based on the same source) and one in CodeGen that > verifies that the code is generated. > > The

On 11/20/2011 04:36 PM, Marcello Maggioni wrote: > Sorry for the noobish question, but what kind of subscripts generate a > SCEVCouldNotCompute from the SCEV engine? > I tried for a while but I wasn't able to trigger that Hi Marcello, the SCEV returns SCEVCouldNotCompute in case it cannot analyze an expression or if the analysis would be to complicated. I am currently not sure if

On 11/21/2011 12:44 PM, Marcello Maggioni wrote: > 2011/11/21 Tobias Grosser<tobias at grosser.es>: >> On 11/20/2011 04:36 PM, Marcello Maggioni wrote: >>> >>> Sorry for the noobish question, but what kind of subscripts generate a >>> SCEVCouldNotCompute from the SCEV engine? >>> I tried for a while but I wasn't able to trigger that >>

2011/11/14 Tobias Grosser <tobias at grosser.es>: > On 11/14/2011 01:24 AM, Marcello Maggioni wrote: >> >> Hi Tobias. >> >> I worked on enabling Polly accepting non affine memory accesses and I >> produced a patch. > > Great. > >> I saw that there were a lot of updates in Polly recently, so I had to >> redo a lot of the work I did and

On Tue, 2011-11-08 at 20:24 +0100, Tobias Grosser wrote: > On 11/08/2011 03:36 PM, Hal Finkel wrote: > > On Tue, 2011-11-08 at 12:12 +0100, Tobias Grosser wrote: > >> On 11/08/2011 11:45 AM, Hal Finkel wrote: > >>> I've attached the latest version of my autovectorization patch. > >>> > >>> Working through the test suite has proved to be a