RFR: 8354242: VectorAPI: combine vector not operation with compare [v6]

[Emanuel Peter]

On Wed, 28 May 2025 12:14:56 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 10 additional commits since the last revision:
>> 
>>  - Refactor the JTReg tests for compare.xor(maskAll)
>>    
>>    Also made a bit change to support pattern `VectorMask.fromLong()`.
>>  - Merge branch 'master' into JDK-8354242
>>  - Refactor code
>>    
>>    Add a new function XorVNode::Ideal_XorV_VectorMaskCmp to do this
>>    optimization, making the code more modular.
>>  - Merge branch 'master' into JDK-8354242
>>  - Update the jtreg test
>>  - Merge branch 'master' into JDK-8354242
>>  - 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	4...
>
> src/hotspot/share/opto/vectornode.cpp line 2244:
> 
>> 2242:   // BoolTest doesn't support unsigned comparisons.
>> 2243:   BoolTest::mask neg_cond =
>> 2244:       (BoolTest::mask) (((VectorMaskCmpNode*) in1)->get_predicate() ^ 4);
> 
> What is the hard-coded `^ 4` here? This whole line looks like we are looking at internals of the `VectorMaskCmpNode` or its predicate, and we should probably do that in some method there? Or maybe it should be part of the `BoolTest(::mask)` interface?

Also: You now cast `(VectorMaskCmpNode*) in1` twice. Can we not do `as_VectorMaskCmp()`? Or could we at least cast it only once, and then use it as `in1_mask_cmp` instead?

> test/hotspot/jtreg/compiler/vectorapi/VectorMaskCompareNotTest.java line 237:
> 
>> 235:     // Byte tests
>> 236:     @Test
>> 237:     @IR(counts = { IRNode.XOR_V_MASK, "= 0", IRNode.XOR_VB, "= 0" },
> 
> Could you still assert the presence of some other vectors, just to make sure we are indeed getting vectors here?

Not testing for any present vectors makes me a little nervous: what if we just don't get any vectors because inlining fails or something else silly happens?

-------------

PR Review Comment: https://git.openjdk.org/jdk/pull/24674#discussion_r2111701943
PR Review Comment: https://git.openjdk.org/jdk/pull/24674#discussion_r2111728478