search for: algabra

...tion is to model the floating point IV in SCEV rather than find a more powerful way of converting the IV to an integer that models the non-integer values taken on by the IV. As an example, if the use case is the following code with appropriate flags to relax IEEE semantics so this looks like normal algabra etc: for (float f = 0.01f; f < 1.0f; f += 0.01f) ... I'd rather see us cleverly turn it into: float f = 0.01f; for (int i = 1; i < 100; i += 1, f += 0.01f) ... (or whatever the transform would be, I've not spent lots of time thinking about the exact way to map this o...

...ing point IV in SCEV rather than > find a more powerful way of converting the IV to an integer that models > > the non-integer values taken on by the IV. As an example, if the use > case is the following code with appropriate flags to relax IEEE > semantics so this looks like normal algabra etc: > > > for (float f = 0.01f; f < 1.0f; f += 0.01f) ç **A** > > ... > > > I'd rather see us cleverly turn it into: > > > float f = 0.01f; > > > for (int i = 1; i < 100; i += 1, f += 0.01f) ç **B** > > I can later try to enhance IndVar...

...is to model the floating point IV in SCEV rather than find a more powerful way of converting the IV to an integer that models > the non-integer values taken on by the IV. As an example, if the use case is the following code with appropriate flags to relax IEEE semantics so this looks like normal algabra etc: > for (float f = 0.01f; f < 1.0f; f += 0.01f) ç **A** ... > I'd rather see us cleverly turn it into: > float f = 0.01f; > for (int i = 1; i < 100; i += 1, f += 0.01f) ç **B** I can later try to enhance IndVarSimplify::handleFloatingPointIV() in order to convert**A**...

...is to model the floating point IV in SCEV rather than find a more powerful way of converting the IV to an integer that models > the non-integer values taken on by the IV. As an example, if the use case is the following code with appropriate flags to relax IEEE semantics so this looks like normal algabra etc: > for (float f = 0.01f; f < 1.0f; f += 0.01f) ç **A** ... > I'd rather see us cleverly turn it into: > float f = 0.01f; > for (int i = 1; i < 100; i += 1, f += 0.01f) ç **B** I can later try to enhance IndVarSimplify::handleFloatingPointIV() in order to convert**A**...

> 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

...ting point IV in SCEV rather than > find a more powerful way of converting the IV to an integer that models > > the non-integer values taken on by the IV. As an example, if the use > case is the following code with appropriate flags to relax IEEE > semantics so this looks like normal algabra etc: > > > for (float f = 0.01f; f < 1.0f; f += 0.01f) ç **A** > > ... > > > I'd rather see us cleverly turn it into: > > > float f = 0.01f; > > > for (int i = 1; i < 100; i += 1, f += 0.01f) ç **B** > > I can later try to enhance IndV...

...ating point IV in SCEV rather than > find a more powerful way of converting the IV to an integer that models >> the non-integer values taken on by the IV. As an example, if the use > case is the following code with appropriate flags to relax IEEE > semantics so this looks like normal algabra etc: > >> for (float f = 0.01f; f < 1.0f; f += 0.01f) ç **A** > > ... > >> I'd rather see us cleverly turn it into: > >> float f = 0.01f; > >> for (int i = 1; i < 100; i += 1, f += 0.01f) ç **B** > > I can later try to enhance IndVarSimplify...

...ail/llvm-dev/2016-September/105108.html >> and http://lists.llvm.org/pipermail/llvm-dev/2017-August/116324.html >> >> +Andrew Trick >> >> — Sanjoy > I was never able to reconcile integrating nsw/nuw flags into SCEV. They violate the spirit of SCEV, in the sense that algabraically equivalent expressions must be uniquely identified, and that the the order that expressions are evaluated should not affect the outcome. > > My understanding matches Hal's, that we can imbue AddRec's with flags because they're already tied to the IR. It's usually incorre...

[+CC Andy] Hi Elena, I don't have any fundamental issues with teaching SCEV about floating point types, but given this will be a major change, I think a high level roadmap should be discussed on llvm-dev before we start reviewing and committing changes. Here are some issues that I think are worth discussing: - Core motivation: why do we even care about optimizing floating point