[llvm] r220345 - LTO: respect command-line options that disable vectorization.

[Alexey Volkov]

Hi JF,

After your commit I saw a performance regression because of disabled Loop
Vectorizer:
 LV: Not vectorizing: No #pragma vectorize enable.
It is really strange since I used -Ofast -flto clang's options to build an
application.
Before this change loop was successfully vectorized by Loop Vectorizer.

Thanks, Alexey.

2014-10-22 3:18 GMT+04:00 JF Bastien <jfb at google.com>:

> Author: jfb
> Date: Tue Oct 21 18:18:21 2014
> New Revision: 220345
>
> URL: http://llvm.org/viewvc/llvm-project?rev=220345&view=rev
> Log:
> LTO: respect command-line options that disable vectorization.
>
> Summary: Patches 202051 and 208013 added calls to LTO's PassManager which
> unconditionally add LoopVectorizePass and SLPVectorizerPass instead of
> following the logic in PassManagerBuilder::populateModulePassManager and
> honoring the -vectorize-loops -run-slp-after-loop-vectorization flags.
>
> Reviewers: nadav, aschwaighofer, yijiang
>
> Subscribers: llvm-commits
>
> Differential Revision: http://reviews.llvm.org/D5884
>
> Modified:
>     llvm/trunk/lib/Transforms/IPO/PassManagerBuilder.cpp
>
> Modified: llvm/trunk/lib/Transforms/IPO/PassManagerBuilder.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/IPO/PassManagerBuilder.cpp?rev=220345&r1=220344&r2=220345&view=diff
>
> ==============================================================================
> --- llvm/trunk/lib/Transforms/IPO/PassManagerBuilder.cpp (original)
> +++ llvm/trunk/lib/Transforms/IPO/PassManagerBuilder.cpp Tue Oct 21
> 18:18:21 2014
> @@ -440,10 +440,12 @@ void PassManagerBuilder::addLTOOptimizat
>    // More loops are countable; try to optimize them.
>    PM.add(createIndVarSimplifyPass());
>    PM.add(createLoopDeletionPass());
> -  PM.add(createLoopVectorizePass(true, true));
> +  PM.add(createLoopVectorizePass(DisableUnrollLoops, LoopVectorize));
>
>    // More scalar chains could be vectorized due to more alias information
> -  PM.add(createSLPVectorizerPass()); // Vectorize parallel scalar chains.
> +  if (RunSLPAfterLoopVectorization)
> +    if (SLPVectorize)
> +      PM.add(createSLPVectorizerPass()); // Vectorize parallel scalar
> chains.
>
>    // After vectorization, assume intrinsics may tell us more about pointer
>    // alignments.
>
>
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-- 
Alexey Volkov
Intel Corporation
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