[llvm-dev] Working on FP SCEV Analysis

Owen Anderson via llvm-dev llvm-dev at lists.llvm.org
Tue May 17 20:49:15 PDT 2016

> On May 16, 2016, at 2:42 PM, Sanjoy Das via llvm-dev <llvm-dev at lists.llvm.org> wrote:
> - Core motivation: why do we even care about optimizing floating
>   point induction variables?  What situations are they common in?  Do
>   programmers _expect_ compilers to optimize them well?  (I haven't
>   worked on our vectorizers so pardon the possibly stupid question)
>   in the example you gave, why do you need SCEV to analyze the
>   increment to vectorize the loop (i.e how does it help)?  What are
>   some other concrete cases you'll want to optimize?

Graphics shading languages like GLSL or HLSL have floating point types as the “default” types.  Integers weren’t even added until later revisions of GLSL.  In that world, it’s not especially strange to imagine a loop counter written in floating point.

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