RFR: 8308606: C2 SuperWord: remove alignment checks when not required [v4]

[Emanuel Peter]

On Wed, 14 Jun 2023 06:24:29 GMT, Fei Gao <fgao at openjdk.org> wrote:

>> Emanuel Peter has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Add vm.flagless back in for LoopArrayIndexComputeTest.java
>
>> Alignment is nice when we can make it happen, as it ensures that we do not have memory accesses across cache lines. But we should not prevent vectorization just because we cannot align all memory accesses for the same memory slice. As the benchmark shows below, we get a good speedup from vectorizing unaligned memory accesses.
> 
> Hi @eme64 , nice rewrite!
> 
> May I ask if you have any benchmark data of misaligned-load-store cases for other data types? For example, `Double` or `Long` on 128-bit machines (maybe aarch64 asimd).

@fg1417 Ok, I will expand the misaligned load-store case for some other data types and test it on my two machines again!

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PR Comment: https://git.openjdk.org/jdk/pull/14096#issuecomment-1590563259