RFR: 8282875: AArch64: [vectorapi] Optimize Vector.reduceLane for SVE 64/128 vector size [v2]

[Andrew Haley]

On Tue, 19 Apr 2022 16:04:06 GMT, Eric Liu <eliu at openjdk.org> wrote:

>> This patch speeds up add/mul/min/max reductions for SVE for 64/128
>> vector size.
>> 
>> According to Neoverse N2/V1 software optimization guide[1][2], for
>> 128-bit vector size reduction operations, we prefer using NEON
>> instructions instead of SVE instructions. This patch adds some rules to
>> distinguish 64/128 bits vector size with others, so that for these two
>> special cases, they can generate code the same as NEON. E.g., For
>> ByteVector.SPECIES_128, "ByteVector.reduceLanes(VectorOperators.ADD)"
>> generates code as below:
>> 
>> 
>>         Before:
>>         uaddv   d17, p0, z16.b
>>         smov    x15, v17.b[0]
>>         add     w15, w14, w15, sxtb
>> 
>>         After:
>>         addv    b17, v16.16b
>>         smov    x12, v17.b[0]
>>         add     w12, w12, w16, sxtb
>> 
>> No multiply reduction instruction in SVE, this patch generates code for
>> MulReductionVL by using scalar insnstructions for 128-bit vector size.
>> 
>> With this patch, all of them have performance gain for specific vector
>> micro benchmarks in my SVE testing system.
>> 
>> [1] https://developer.arm.com/documentation/pjdoc466751330-9685/latest/
>> [2] https://developer.arm.com/documentation/PJDOC-466751330-18256/0001
>> 
>> Change-Id: I4bef0b3eb6ad1bac582e4236aef19787ccbd9b1c
>
> Eric Liu has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Generate SVE reduction for MIN/MAX/ADD as before
>   
>   Change-Id: Ibc6b9c1f46c42cd07f7bb73b81ed38829e9d0975

src/hotspot/cpu/aarch64/aarch64_sve_ad.m4 line 2179:

> 2177: %}
> 2178: 
> 2179: 

This is all far too repetitive and (therefore) hard to maintain. Please use the macro processor in a sensible way.

Please isolate the common factors.
`n->in(X)->bottom_type()->is_vect()->length_in_bytes()` should have a name, for example.

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PR: https://git.openjdk.java.net/jdk/pull/7999