[llvm-dev] Loop identification

Krzysztof Parzyszek via llvm-dev llvm-dev at lists.llvm.org
Fri Jan 13 10:53:01 PST 2017

On 1/13/2017 10:52 AM, Hal Finkel wrote:
> but I think we need to discuss the use case.

The main case for us was recognizing polynomial multiplications. Hexagon 
has instructions that do that, and the goal was to replace loops that do 
that with intrinsics. The problem is that these loops often get unrolled 
and intertwined with other code, making the replacement hard, or 
impossible. This is especially true if some of the multiplication code 
is combined with instructions that were not originally part of it (I 
don't remember 100% if that was happening, but the loop optimizations 
were the main culprit in making it hard).


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