similar to: SCEV LoopTripCount

Ok. To go back to the original issue, would it be meaningful to add a SCEVUMax(0, BTC) on the final BTC computed by SCEV? So that it does not use "negative values"? On Wed, Aug 15, 2018 at 2:40 PM Friedman, Eli <efriedma at codeaurora.org> wrote: > On 8/15/2018 2:27 PM, Alexandre Isoard wrote: > > I'm not sure I understand the poison/undef/UB distinctions. >

I'm not sure I understand the poison/undef/UB distinctions. But on this example: define i32 @func(i1 zeroext %b, i32 %x, i32 %y) { > entry: > %adds = add nsw i32 %x, %y > %addu = add nuw i32 %x, %y > %cond = select i1 %b, i32 %adds, i32 %addu > ret i32 %cond > } It is important to not propagate the nsw/nuw between the two SCEV expressions (which unification would

Is that why we do not deduce +<nsw> from "add nsw" either? Is that an intrinsic limitation of creating a context-invariant expressions from a Value* or is that a limitation of our implementation (our unification not considering the nsw flags)? On Wed, Aug 15, 2018 at 12:39 PM Friedman, Eli <efriedma at codeaurora.org> wrote: > On 8/15/2018 12:21 PM, Alexandre Isoard via

Hello, If I run clang on the following code: void func(unsigned n) { > for (unsigned long x = 1; x < n; ++x) > dummy(x); > } I get the following llvm ir: define void @func(i32 %n) { > entry: > %conv = zext i32 %n to i64 > %cmp5 = icmp ugt i32 %n, 1 > br i1 %cmp5, label %for.body, label %for.cond.cleanup > for.cond.cleanup:

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

Hello. I tried to get the trip count of a loop with Scalar evolution. I got inspired from http://stackoverflow.com/questions/13834364/how-to-get-loop-bounds-in-llvm . However the analysis described there doesn't work well for the second inner loop of thes function below (although if we declare Bcols a short it works well): void MatMul(int Arows, int Acols, int Brows, int

Hello, I am first time paying with SCEV codebase. I am trying to find out why ScalarEvolution is not able to give correct back edge taken count for an expression. So in my case flow reaches to howFarToZero() and in that function, I have following expressions as SCEV Start = (15 + (-1 * %i) (which is set to Distance SCEV) Step = 1 now, first of all, should I expect Start as ConstantSCEV (15)

If count > MAX_UINT-4 your loop loops indefinitely with an increment of 4, I think. On Thu, Oct 13, 2016 at 4:42 PM, Charith Mendis via llvm-dev < llvm-dev at lists.llvm.org> wrote: > So, I tried unrolling the following simple loop. > > int unroll(unsigned * a, unsigned * b, unsigned *c, unsigned count){ > > for(unsigned i=0; i<count; i++){ > > a[i] =

Hello, I assumed SCEV purpose was to be a normal form, but then I wondered which one of those is the normal form: (zext i16 (trunc i32 %a to i16) to i32) vs (-((%a /u 65536) *u 65536) + %a) The first one is nice for interval analysis, and known bit analysis. The second one is nice when plugged into gep of 2d arrays. -- *Alexandre Isoard* -------------- next part -------------- An HTML

Note that there is a slight difficulty due to the fact that we "sink" the trunc: (zext i16 {0,+,1}<%bb> to i32) + (65536 * ({0,+,1}<nuw><%bb> /u 65536) Here the recurrence lost it's <nuw> and got reduced to a i16 (on the left), but not on the right. But we can prove: - that (zext i16 {0,+,1}<%bb> to i32) has the same 16 LSB than (i32

Hi everyone, I'm having some trouble with my ifelse statements. I'm trying to put 12 conditions within 3 groups. Here is the code I have so far: dat$cond <- ifelse(test = dat$cond == "cond1" | dat$cond == "cond2" | dat$cond == "cond3" dat$cond == "cond4" yes = "Uniform" no = ifelse(test =

Hello, I was thinking about printing SCEV into DiagnosticInfo messages, an example would be to print the loop trip count of loops, or the stride of memory accesses. I ran into two problems: - DiagnosticInfo is in Core, SCEV is in Analysis, so it is a little bit weird (I declare the operator<< overload for SCEV* in DiagnosticInfo, but only define it in ScalarEvolution) - I would like to

Hi all, It looks like the induction variable simplification pass prefers doing a zero-extension to compute the wider trip count of loops when extending the IV. This can sometimes result in loss of information making ScalarEvolution's analysis conservative which can lead to missed performance opportunities. For example, consider this loopnest- int i, j; for(i=0; i< 40; i++) for(j=0;

Hello, Is there a way to dump the Module IR with the SCEV as comment at the end of each line? The -analyze or -debug-pass is not printed on the IR itself. Maybe through the DiagnosticInfo? -- *Alexandre Isoard* -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20180322/e178b4c8/attachment.html>

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 Deepali, SCEV reports the backedge taken count as "((-1 * (sext i32 (3 + %x) to i64))<nsw> + ((sext i32 (3 + %x) to i64) smax (sext i32 (6 + %x) to i64)))", so symbolically it does have an answer. Ideally SCEV should be able to exploit <nsw> on (3 + %x) and (6 + %x) to fold the expression above to "3", but due to some systemic issues SCEV can't exploit

On 3/22/2018 6:29 PM, Alexandre Isoard via llvm-dev wrote: > Hello, > > Is there a way to dump the Module IR with the SCEV as comment at the > end of each line? AssemblyAnnotationWriter exists, but I don't think anyone has hooked it up to SCEV, specifically. -Eli -- Employee of Qualcomm Innovation Center, Inc. Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,

Thanks for the explanation. But I am a little confused with the following fact. Can't LLVM keep vectorizable_elements as a symbolic value and convert the loop to say; for(unsigned i = 0; i < vectorizable_elements ; i += 2){ //main loop } for(unsigned i=0 ; i < vectorizable_elements % 2; i++){ //fix up } Why does it have to reason about the range of vectorizable_elements? Even

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

Hello Everyone, I want to raise a discussion about reasonability of late setting of nsw/nuw/nw flags to SCEV AddRecs through setNoWrapFlags method. A discussion about this have already happened in August last year, there was a concern about different no-wrap flags that come from different sequences of SCEV flags invocations. It was mentioned there that late setting of flags is actually a hack to