[PATCH] D93929: [NewPM][Hexagon] Fix HexagonVectorLoopCarriedReusePass position in pipeline

[Arthur Eubanks via Phabricator via llvm-commits]

aeubanks added a comment.

In D93929#2485715 <https://reviews.llvm.org/D93929#2485715>, @quic_aankit wrote:

> @asbirlea I remember that HexagonVLCR pass has a dependency on LCSSA and LoopSimplifyPass. Is there any way we can run these passes too at LoopOptimizerEndEP? If not maybe use another EP for legacy PM? I'm not sure if the below code would run these passes in the correct order as well
>
>   PB.registerOptimizerLastEPCallback(
>       [=](ModulePassManager &MPM, PassBuilder::OptimizationLevel Level) {
>         LoopPassManager LPM(DebugPassManager);
>         FunctionPassManager FPM(DebugPassManager);
>         LPM.addPass(HexagonVectorLoopCarriedReusePass());
>         FPM.addPass(LoopSimplifyPass());
>         FPM.addPass(LCSSAPass());
>         FPM.addPass(createFunctionToLoopPassAdaptor(std::move(LPM)));
>         MPM.addPass(createModuleToFunctionPassAdaptor(std::move(FPM)));
>       });
>
> @pranavb Can you comment more on this?

LCSSA should be preserved by all loop passes under the new PM. LCSSA and LoopSimplify are run before any loop pass: https://github.com/llvm/llvm-project/blob/8dddcc762dd98d53b9406b36e92f62502834187c/llvm/include/llvm/Transforms/Scalar/LoopPassManager.h#L406. Although I don't think passes are required preserve loop simplify form.


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