search for: isscevexprneverpoison

> 1. Callers are expected to not engage in speculation. ScalarEvolution > itself must only create expressions it knows hold in all cases. This is correct. There is some more relevant text in ScalarEvolution::isSCEVExprNeverPoison. And you're right, this is quite restrictive. > Long term, I think that it would be cleaner to rework this so that all of the SCEV's are immutable and include their flags. I proposed this in 2016 but Andy had some concerns and I dropped it. See http://lists.llvm.org/pipermail/llvm-dev...

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

> On Jun 29, 2017, at 4:39 AM, Hal Finkel <hfinkel at anl.gov> wrote: > > On 06/28/2017 05:33 PM, Peter Lawrence wrote: >> Chandler, >> where we disagree is in whether the current project is moving the issue >> forward. It is not. It is making the compiler more complex for no additional value. >> >> The current project is not based in

...joy at playingwithpointers.com> wrote: >> >>> 1. Callers are expected to not engage in speculation. ScalarEvolution >>> itself must only create expressions it knows hold in all cases. >> This is correct. There is some more relevant text in >> ScalarEvolution::isSCEVExprNeverPoison. And you're right, this is >> quite restrictive. >> >>> Long term, I think that it would be cleaner to rework this so that all of the SCEV's are immutable and include their flags. >> I proposed this in 2016 but Andy had some concerns and I dropped it. >> Se...

Hi, I'm working on a bug somewhere between SCEV and IndVarSimplify, which tacks an unwanted "nuw" onto an "add i32 %whatever, -1" (which actually almost certainly will overflow), leading ultimately to an infinite loop. A fuller description and test-case is at the end for anyone interested. The issue seems to be with ScalarEvolution's attempts to cache SCEV objects,