RFR: 8342103: C2 compiler support for Float16 type and associated scalar operations [v3]

[Jatin Bhateja]

On Mon, 16 Dec 2024 09:03:38 GMT, Emanuel Peter <epeter at openjdk.org> wrote:

> > > Can you quickly summarize what tests you have, and what they test?
> > 
> > 
> > Patch includes functional and performance tests, as per your suggestions IR framework-based tests now cover various special cases for constant folding transformation. Let me know if you see any gaps.
> 
> I was hoping that you could make a list of all optimizations that are included here, and tell me where the tests are for it. That would significantly reduce the review time on my end. Otherwise I have to correlate everything myself, and that will take me hours.


Validations details:-

A) x86 backend changes
   - new assembler instruction
   - macro assembly routines. 
    Test point:-  test/jdk/jdk/incubator/vector/ScalarFloat16OperationsTest.java
         - This test is based on a testng framework and includes new DataProviders to generate test vectors.
         -  Test vectors cover the entire float16 value range and also special floating point values (NaN, +Int, -Inf, 0.0 and -0.0) 
B) GVN transformations:-
     -  Value Transforms
        Test point:- test test/hotspot/jtreg/compiler/c2/irTests/TestFloat16ScalarOperations.java
              -  Covers all the constant folding scenarios for add, sub, mul, div, sqrt, fma, min, and max operations addressed by this patch.
              -  It also tests special case scenarios for each operation as specified by Java language specification.
    -   identity Transforms
        Test point:- test test/hotspot/jtreg/compiler/c2/irTests/TestFloat16ScalarOperations.java
               -  Covers identity transformation for  ReinterpretS2HFNode,  DivHFNode
    -  idealization Transforms
        Test points:-  test/hotspot/jtreg/compiler/c2/irTests/MulHFNodeIdealizationTests.java
                                :-   test test/hotspot/jtreg/compiler/c2/irTests/TestFloat16ScalarOperations.java
            - Contains test point for the following transform 
                         MulHF idealization i.e. MulHF * 2 => AddHF  
           -  Contains test point for the following transform
                         DivHF SRC ,  PoT(constant) =>  MulHF SRC * reciprocal (constant) 
            - Contains idealization test points for the following transform 
                   ConvF2HF(FP32BinOp(ConvHF2F(x), ConvHF2F(y))) =>
                           ReinterpretHF2S(FP16BinOp(ReinterpretS2HF(x), ReinterpretS2HF(y)))

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PR Comment: https://git.openjdk.org/jdk/pull/22754#issuecomment-2545754021