similar to: Question on induction variable simplification pass

Hi Sanjoy, I have attached the IR I got by compiling with -O2. This is just before we widen the IV. To get the backedge taken count info I ran indvars on it and then replaced zext with sext. I think regardless of where we decide to add this transformation in the pipeline, it should try to preserve as much information as it can. This means that we should generate sext for signed IVs and

Hi Pankaj, On April 14, 2017 at 4:55:16 PM, Chawla, Pankaj (pankaj.chawla at intel.com) wrote: > I have attached the IR I got by compiling with -O2. This is just before we widen the IV. Thanks! > To get the backedge taken count info I ran indvars on it and then replaced zext with sext. > > I think regardless of where we decide to add this transformation in the pipeline, it should

Thanks for the suggestion but datalayout info did not solve the problem! -Pankaj -----Original Message----- From: Philip Reames <listmail at philipreames.com> Sent: Tuesday, August 20, 2019 5:26 PM To: Chawla, Pankaj <pankaj.chawla at intel.com>; llvm-dev at lists.llvm.org Subject: Re: [llvm-dev] missing simplification in ScalarEvolution? Try adding a datalayout with pointer size

Hi Sanjoy, Thanks for the reply! Your approach sounds good to me! I think 1) is legal as address wraparound in unsigned range doesn't make sense given a positive offset, but I am not sure. I think umax will not be added if we can prove the predicate as known. I am not sure whether umax will get simplified if we add nuw to the expressions. -Pankaj -----Original Message----- From: Sanjoy

Hi, I have this small test case- %struct1 = type { i32, i32 } @glob_const = internal constant [4 x %struct1] [%struct1 { i32 4, i32 5 }, %struct1 { i32 8, i32 9 }, %struct1 { i32 16, i32 0 }, %struct1 { i32 32, i32 10 }], align 16 define void @foo() { entry: br label %loop loop: ; preds = %loop, %entry %iv = phi %struct1* [ getelementptr

Hi, It looks like ScalarEvolution bails out of loop backedge computation if it cannot prove the IV stride as either positive or negative (based on loop control condition). I think this logic can be refined for signed IVs. Consider this simple loop- void foo(int *A, int n, int s) { int i; for(i=0; i<n; i += s) { A[i]++; } } The IV of this loop has this SCEV form-

Hi Pankaj, Chawla, Pankaj via llvm-dev wrote: > It looks like ScalarEvolution bails out of loop backedge computation if > it cannot prove the IV stride as either positive or negative (based on > loop control condition). I think this logic can be refined for signed IVs. > > Consider this simple loop- > > void foo(int *A, int n, int s) { > > int i; > >

Hi Sanjoy, SCEV is behaving inconsistently when forming SCEV for this zext instruction in the attached test case- %conv5 = zext i32 %dec to i64 If we request a SCEV for the instruction, it returns- (zext i32 {{-1,+,1}<nw><%for.body>,+,-1}<nw><%for.body7> to i64) This can be seen by invoking- $ opt -analyze -scalar-evolution inconsistent-scev-zext.ll But when computing

Hi, +CC Max, Serguei This looks like a textbook case of why caching is hard. We first call getZeroExtendExpr on %dec, and this call does end up returning an add rec. However, in the process of simplifying the zext, it also calls into isLoopBackedgeGuardedByCond which in turn calls getZeroExtendExpr(%dec) again. However, this second (recursive) time, we don't simplify the zext and cache a

Hi, I noticed an inconsistency in how ScalarEvolution orders instruction operands. This inconsistency can result in creation of separate (%a * %b) and (%b * %a) SCEVs as demonstrated by the example IR below (attached as gep-phi.ll)- target datalayout = "e-m:e-p:32:32-f64:32:64-f80:32-n8:16:32-S128" define void @foo(i8* nocapture %arr, i32 %n, i32* %A, i32* %B) local_unnamed_addr {

----- Original Message ----- > From: "Chandler Carruth" <chandlerc at google.com> > To: "Hal Finkel" <hfinkel at anl.gov> > Cc: "Hyojin Sung" <hsung at us.ibm.com>, llvmdev at cs.uiuc.edu > Sent: Thursday, July 16, 2015 1:06:03 AM > Subject: Re: [LLVMdev] Improving loop vectorizer support for loops > with a volatile iteration

----- Original Message ----- > From: "Chandler Carruth" <chandlerc at google.com> > To: "Hyojin Sung" <hsung at us.ibm.com>, llvmdev at cs.uiuc.edu > Sent: Wednesday, July 15, 2015 7:34:54 PM > Subject: Re: [LLVMdev] Improving loop vectorizer support for loops > with a volatile iteration variable > On Wed, Jul 15, 2015 at 12:55 PM Hyojin Sung

Hi Sanjoy, Thanks for investigating the issue! I am more interested in getting the underlying problem fixed rather than making this particular test case work. I think I have more test cases where this problem crops up. I would any day prefer consistent results over compile time savings which can lead to inconsistencies. These inconsistencies require significant developer time to analyze and fix

----- Original Message ----- > From: "Hal Finkel" <hfinkel at anl.gov> > To: "Chandler Carruth" <chandlerc at google.com> > Cc: llvmdev at cs.uiuc.edu > Sent: Thursday, July 16, 2015 1:58:02 AM > Subject: Re: [LLVMdev] Improving loop vectorizer support for loops > with a volatile iteration variable > ----- Original Message ----- > >

Hi Gerolf, I think we have several (perhaps separable) issues here: 1. Do we have a canonical form for loops, preserved through the optimizer, that allows naturally-constructed loop nests to remain separable? 2. Do we forbid non-lowering transformations that turn vectorizable loops into non-vectorizable loops? 3. How do we detect cases where transformations cause a negative answer to either

Thanks for fixing this Sanjoy! I do have a few questions/suggestions on the fix if you don't mind. 1) Would this work correctly if the values are call instructions with no operands, like this- %a = foo() %b = bar() 2) From the way this function is set up, it looks like the emphasis is on saving compile time by trading off robustness. Is compile time such a big concern here that we want to

This sounds fine to me (and sorry for the delay!). -- Sanjoy On Mon, Mar 12, 2018 at 1:09 PM, Chawla, Pankaj <pankaj.chawla at intel.com> wrote: > Hi Sanjoy, > > So what is the verdict on this issue? > > Thanks, > Pankaj > > > -----Original Message----- > From: Chawla, Pankaj > Sent: Monday, February 26, 2018 11:12 AM > To: Sanjoy Das <sanjoy at

Thanks for the helpful reply! I see that we are trying to keep ScalarEvolution stable around instruction ordering. My suggestion would be to not restrict the fix by only recursing on the first operand. By "dominator logic" I meant that if all other 'cheap' checks fail, we should decide by walking the dominator tree to see which instruction's basic block is encountered

Here is original C code: void topup(int a[], unsigned long i) { for (; i < 16; i++) { a[i] = 1; } } Here is the IR before the pass where I expect SCEV to return trip-count value ; Function Attrs: nofree norecurse nounwind uwtable writeonly define dso_local void @topup(i32* nocapture %a, i64 %i) local_unnamed_addr #0 { entry: %cmp3 = icmp ult i64 %i, 16 br i1

Hi Pankaj, On Tue, Mar 13, 2018 at 1:55 PM, Chawla, Pankaj <pankaj.chawla at intel.com> wrote: > Thanks for the reply! > Would it be possible for you to implement this? I don't have cycles for this right now, but if you file a bug I can give this a shot when I have time later. Even in the best case this will have to at least wait until end of April because I'm leaving for a