[llvm-dev] Working on FP SCEV Analysis

Demikhovsky, Elena via llvm-dev llvm-dev at lists.llvm.org
Wed May 18 06:25:28 PDT 2016

> Even then, I'd personally want to see further evidence of why the correct solution 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)  <== *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) <== *B*

I can later try to enhance IndVarSimplify::handleFloatingPointIV() in order to convert *A* to *B*.
But *B* is exactly the case I’m starting from. The main IV “i” is integer. The variable “f” is also considered as IV in this loop.
And this loop is not vectorized because “f” is floating point.
I don’t think that the case *B* is uncommon.

-           Elena
Intel Israel (74) Limited

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