RFR: 8325438: Add exhaustive tests for Math.round intrinsics

[Emanuel Peter]

On Thu, 8 Feb 2024 18:07:28 GMT, Vladimir Kozlov <kvn at openjdk.org> wrote:

>> HI,
>> Can you have a look at this patch adding some tests for Math.round instrinsics?
>> Thanks!
>> 
>> ### FYI:
>> During the development of RoundVF/RoundF, we faced the issues which were only spotted by running test exhaustively against 32/64 bits range of int/long.
>> It's helpful to add these exhaustive tests in jdk for future possible usage, rather than build it everytime when needed.
>> Of course, we need to put it in `manual` mode, so it's not run when `-automatic` jtreg option is specified which I guess is the mode CI used, please correct me if I'm assume incorrectly.
>
> test/hotspot/jtreg/compiler/c2/cr6340864/TestDoubleVectManual.java line 100:
> 
>> 98:           for (int sign = 0; sign < 2; sign++) {
>> 99:             int idx = ei*2+sign;
>> 100:             if (res[idx] != Math.round(input[idx])) {
> 
> You are comparing `Math.round()` with `Math.round()` results.  It is possible that C2 will compile `test()` too as OSR.
> I would suggest to move code which creates "golden" values into a separate method and exclude it from compilation. To run code in Interpreter.

@vnkozlov @Hamlin-Li 
We hope to improve the IR test framework soon to implicitly do "golden" value tests: https://bugs.openjdk.org/browse/JDK-8310533

Until that is all in place, you should do it like in this test:
`test/hotspot/jtreg/compiler/vectorization/TestOptionVectorizeIR.java`
(you can see the `gold` values, and the `@IR` rules)

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PR Review Comment: https://git.openjdk.org/jdk/pull/17753#discussion_r1483891153