RFR: 8354242: VectorAPI: combine vector not operation with compare [v3]

[erifan]

On Tue, 29 Apr 2025 10:22:22 GMT, Emanuel Peter <epeter at openjdk.org> wrote:

>> erifan has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains four additional commits since the last revision:
>> 
>>  - Addressed some review comments
>>    
>>    1. Call VectorNode::Ideal() only once in XorVNode::Ideal.
>>    2. Improve code comments.
>>  - Merge branch 'master' into JDK-8354242
>>  - Merge branch 'master' into JDK-8354242
>>  - 8354242: VectorAPI: combine vector not operation with compare
>>    
>>    This patch optimizes the following patterns:
>>    For integer types:
>>    ```
>>    (XorV (VectorMaskCmp src1 src2 cond) (Replicate -1))
>>        => (VectorMaskCmp src1 src2 ncond)
>>    (XorVMask (VectorMaskCmp src1 src2 cond) (MaskAll m1))
>>        => (VectorMaskCmp src1 src2 ncond)
>>    ```
>>    cond can be eq, ne, le, ge, lt, gt, ule, uge, ult and ugt, ncond is the
>>    negative comparison of cond.
>>    
>>    For float and double types:
>>    ```
>>    (XorV (VectorMaskCast (VectorMaskCmp src1 src2 cond)) (Replicate -1))
>>        => (VectorMaskCast (VectorMaskCmp src1 src2 ncond))
>>    (XorVMask (VectorMaskCast (VectorMaskCmp src1 src2 cond)) (MaskAll m1))
>>        => (VectorMaskCast (VectorMaskCmp src1 src2 ncond))
>>    ```
>>    cond can be eq or ne.
>>    
>>    Benchmarks on Nvidia Grace machine with 128-bit SVE2:
>>    With option `-XX:UseSVE=2`:
>>    ```
>>    Benchmark			Unit	Before		Score Error	After		Score Error	Uplift
>>    testCompareEQMaskNotByte	ops/s	7912127.225	2677.289518	10266136.26	8955.008548	1.29
>>    testCompareEQMaskNotDouble	ops/s	884737.6799	446.963779	1179760.772	448.031844	1.33
>>    testCompareEQMaskNotFloat	ops/s	1765045.787	682.332214	2359520.803	896.305743	1.33
>>    testCompareEQMaskNotInt		ops/s	1787221.411	977.743935	2353952.519	960.069976	1.31
>>    testCompareEQMaskNotLong	ops/s	895297.1974	673.44808	1178449.02	323.804205	1.31
>>    testCompareEQMaskNotShort	ops/s	3339987.002	3415.2226	4712761.965	2110.862053	1.41
>>    testCompareGEMaskNotByte	ops/s	7907615.16	4094.243652	10251646.9	9486.699831	1.29
>>    testCompareGEMaskNotInt		ops/s	1683738.958	4233.813092	2352855.205	1251.952546	1.39
>>    testCompareGEMaskNotLong	ops/s	854496.1561	8594.598885	1177811.493	521.1229	1.37
>>    testCompareGEMaskNotShort	ops/s	3341860.309	1578.975338	4714008.434	1681.10365	1.41
>>    testCompareGTMaskNotByte	ops/s	7910823.674	2993.367032	10245063.58	9774.75138	1.29
>>    testCompareGTMaskNotInt		ops/s	1673393...
>
> Yes, this discussion is down to `requires` vs `applyIf`. This is my argument for `applyIf`, quoted from above, I have not yet seen an argument against it:
> 
>>  If you use @require, then the person does not realize there is a test AND the test is not run. If you use applyIf, the person does not realize there is a test, but it is run at least for result verifiation - and then the person MIGHT realize if the test catches a wrong result / crash.
> 
> In my understanding, `requires` should only be used if the test really **requires** a certain platform or feature. That can be because some flags are only available under certain platforms for example. But for IR tests, we should try to always use `applyIf`, because it allows testing on other platforms.
> 
> Actually, I filed this RFE a while ago: https://bugs.openjdk.org/browse/JDK-8310891
> We should try to move as many tests from using `requires` to `applyIf`, so that we have an increased test coverage.

@eme64 @jatin-bhateja I have updated the test, thanks for your suggestion.

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PR Comment: https://git.openjdk.org/jdk/pull/24674#issuecomment-2844256626