[PATCH] D118979: [AArch64] Set maximum VF with shouldMaximizeVectorBandwidth

Thu Feb 10 04:00:43 PST 2022

paulwalker-arm added a comment.

In D118979#3310625 <https://reviews.llvm.org/D118979#3310625>, @jaykang10 wrote:

> In D118979#3310489 <https://reviews.llvm.org/D118979#3310489>, @paulwalker-arm wrote:
>
>> So I'm wondering why we don't just control the functionality with a default off command line flag.  That way it's available for testing, including unit-tests, until such a point where code generation is at a point where is makes sense to default it to on. Is this a terribly idea?
>
> There is an option `-vectorizer-maximize-bandwidth` to control the functionality in LV.
>
>   static cl::opt<bool> MaximizeBandwidth(
>       "vectorizer-maximize-bandwidth", cl::init(false), cl::Hidden,
>       cl::desc("Maximize bandwidth when selecting vectorization factor which "
>                "will be determined by the smallest type in loop."));

Oh sure, but that affects all targets.  Whereas I thought here we're talking about finding a migration path to enable it by default for AArch64 only.

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https://reviews.llvm.org/D118979