similar to: [LLVMdev] SCEV not simplifying

Hi, So SCEV cannot simplify that expression to -1 because of overflow issues (take e.g. src=0x7FFF..). If you compile with 64 bits integers, then the sexts disappear and so SCEV can do the simplification. Depending on what you want to do, you may want to either do not extend src and dst to 64 bits or add a NSW flag to the computations. That will hopefully make SCEV push the sext outside and

On Tue, Sep 18, 2012 at 10:59 PM, Andrew Trick <atrick at apple.com> wrote: > > On Sep 18, 2012, at 8:21 PM, Preston Briggs <preston.briggs at gmail.com> > wrote: > > Given the following SCEV, > > *(sext i32 {2,+,1}<nw><%for.body> to i64)* > > > from the following C source, > > *void strong3(int *A, int *B, int n) {* > * for (int i =

On Wed, Sep 19, 2012 at 6:30 PM, Andrew Trick <atrick at apple.com> wrote: > > On Sep 19, 2012, at 2:18 PM, Preston Briggs <preston.briggs at gmail.com> > wrote: > > On Tue, Sep 18, 2012 at 10:59 PM, Andrew Trick <atrick at apple.com> wrote: > >> >> On Sep 18, 2012, at 8:21 PM, Preston Briggs <preston.briggs at gmail.com> >> wrote:

On Sep 19, 2012, at 2:18 PM, Preston Briggs <preston.briggs at gmail.com> wrote: > On Tue, Sep 18, 2012 at 10:59 PM, Andrew Trick <atrick at apple.com> wrote: > > On Sep 18, 2012, at 8:21 PM, Preston Briggs <preston.briggs at gmail.com> wrote: > >> Given the following SCEV, >> >> (sext i32 {2,+,1}<nw><%for.body> to i64) >>

Given the following SCEV, *(sext i32 {2,+,1}<nw><%for.body> to i64)* from the following C source, *void strong3(int *A, int *B, int n) {* * for (int i = 0; i < n; i++) {* * A[i + 2] = i;* * ...* * }* *}* Since the No-Wrap flag is set on the addrec, can't I safely rewrite it as *{2,+,1}<nw><%for.body>* If I can, why isn't the SCEV package

On Sep 18, 2012, at 8:21 PM, Preston Briggs <preston.briggs at gmail.com> wrote: > Given the following SCEV, > > (sext i32 {2,+,1}<nw><%for.body> to i64) > > from the following C source, > > void strong3(int *A, int *B, int n) { > for (int i = 0; i < n; i++) { > A[i + 2] = i; > ... > } > } > > Since the No-Wrap flag is

Thanks for your insides Sanjoy! I don't really believe that option 2 may work just because even if we recalculate the range for this add recurrency, there are already its derivatives with cached ranges (the most obvious example is sext and expressions where this sext is involved). We can speculate about what is "simple enough" to not cache the ranges, but I believe that there is

On Thu, Jan 25, 2018 at 9:55 PM, Maxim Kazantsev <max.kazantsev at azul.com> wrote: > I don't really believe that option 2 may work just because even if we recalculate the range for this add recurrency, there are already its derivatives with cached ranges (the most obvious example is sext and expressions where this sext is involved). We can speculate about what is "simple

Hi Max, On Wed, Jan 24, 2018 at 10:03 PM, Maxim Kazantsev via llvm-dev <llvm-dev at lists.llvm.org> wrote: > 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

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

On 11/02/2012 10:21 AM, Preston Briggs wrote: > > My initial guess is that a conservative fix is quick and small (make > sure the underlying pointers are loop invariant, otherwise give up). A > better approach would be to somehow turn code like the example into > array references that can be analyzed. I'll need to think about this and > do some reading. Hi Preston, I looked

On 11/02/2012 11:02 AM, Hal Finkel wrote: > ----- Original Message ----- >> From: "Tobias Grosser" <tobias at grosser.es> >> To: "preston briggs" <preston.briggs at gmail.com> >> Cc: "Benjamin Kramer" <benny.kra at gmail.com>, "LLVM Developers Mailing List" <llvmdev at cs.uiuc.edu> >> Sent: Friday, November

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

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

Hi, > Sorry, I probably led you astray. No-self-wrap is useful for determining > trip count, but does not mean that sign/zero extension can be hoisted. > > But if you run your analysis after -indvars, the sign-extension should be > removed if possible. The algorithm walks the derived induction variables > specifically looking for add nsw/nuw and replacing

Here's the current code (abstracted a bit) const Instruction *Src, const Instruction *Dst, // make sure they are loads and stores, then const Value *SrcPtr = getPointerOperand(Src); // hides a little casting, then Src->getPointerOperand const Value *DstPtr = getPointerOperand(Dst); // ditto // see how underlying objects alias, then const GEPOperator *SrcGEP =

When compile the following case and look at the SCEV analysis, I notice that the first two loops don't have a LoopInvariantBackedgeTakenCount (surprising) and the last one does (not surprising, except in the context of the first two examples). *void p4(int *A, int *B, long int n) {* * for (char i = 0; i < n; i++) {* * A[i + 2] = i;* * *B++ = A[i];* * }* *}* * * *void p5(int *A, int

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

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

----- Original Message ----- > From: "Tobias Grosser" <tobias at grosser.es> > To: "preston briggs" <preston.briggs at gmail.com> > Cc: "Benjamin Kramer" <benny.kra at gmail.com>, "LLVM Developers Mailing List" <llvmdev at cs.uiuc.edu> > Sent: Friday, November 2, 2012 12:56:53 PM > Subject: Re: [LLVMdev]