On Tue, 2 Dec 2025 01:09:59 GMT, Chen Liang <[email protected]> wrote:
>> test/hotspot/jtreg/compiler/c2/irTests/TestGetAndAdd.java line 78:
>>
>>> 76: @IR(counts = {IRNode.X86_LOCK_XADDB, "3"}, phase =
>>> CompilePhase.FINAL_CODE)
>>> 77: public static void addB() {
>>> 78: var _ = (byte) B.getAndAdd(b2);
>>
>>> Since I removed the return type dropping VarHandle bypass, TestGetAndAdd
>>> became affected because it can no longer access the x86 assembly.
>>
>> It has performance implications for user code, doesn't it?
>
> The performance is measured by the existing
> `org.openjdk.bench.java.lang.invoke.VarHandleExact` benchmark, which
> originally expects `generic_genericInvocation` to be much slower. Now it
> instead has a performance on par with the exact invocations.
>
> The constant folding ability is verified with the new
> `VarHandleMismatchedTypeFold` IR test.
If I understand the IR test logic correctly, C2 was able to compile `(void)
B.getAndAdd(b2)` call down to the desired instruction sequence. Is it still the
case after the fix? What happens if you keep `TestGetAndAdd.java
` intact?
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PR Review Comment: https://git.openjdk.org/jdk/pull/28585#discussion_r2579300293
