[vectorIntrinsics] RFR: Add utf8 decoding benchmarks

[Paul Sandoz]

On Wed, 25 Nov 2020 21:25:25 GMT, Paul Sandoz <psandoz at openjdk.org> wrote:

>> @luhenry Looks good to me as well. Please do create a separate branch (other than vectorIntrinsics) as indicated above by OpenJDK Skara bot and resubmit the pull request from the new branch.
>
> This benchmark has identified a few issues:
> 
> 1. Operations on species of byte/64 are not intrinsic.
> 2. `ShortVector` from/to char[] are not intrinsic (i suspected this to be the case).
> 
> For now:
> 
> 1) can be unblocked by focusing on byte/128 and short/256.
> 2) can be unblocked with the following patch (so it appears, but needs more detailed review) or using `short[]`.
> 
> diff --git a/src/hotspot/share/opto/vectorIntrinsics.cpp b/src/hotspot/share/opto/vectorIntrinsics.cpp
> index db7b69a9137..399130b0e45 100644
> --- a/src/hotspot/share/opto/vectorIntrinsics.cpp
> +++ b/src/hotspot/share/opto/vectorIntrinsics.cpp
> @@ -624,7 +624,10 @@ bool LibraryCallKit::inline_vector_mem_operation(bool is_store) {
>    // Handle loading masks.
>    // If there is no consistency between array and vector element types, it must be special byte array case or loading masks
>    if (arr_type != NULL && !using_byte_array && elem_bt != arr_type->elem()->array_element_basic_type() && !is_mask) {
> -    return false;
> +    if (elem_bt == T_SHORT && arr_type->elem()->array_element_basic_type() == T_CHAR) {
> +    } else {
> +      return false;
> +    }
>    }
> 
> In general, to found the causes of issues i recommend extracting out vector sub-expressions and placing in separate benchmarks. It's easier to analyze the code that is generated.
> 
> The benchmark is also storing vectors/shuffles on the heap. Instead i recommend storing such data in compatible arrays, then loading into vector instances held in local variables.

Clarifications on byte/64 operations are not intrinsic. I was just focusing on the `decodeVectorASCII` benchmark. I think it is specifically due to the mask operations.

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PR: https://git.openjdk.java.net/panama-vector/pull/26