RFR JDK-8207219: [lworld] C2 should not invoke a method if its signature has inconsistent use of ValueType (original) (raw)

Ioi Lam ioi.lam at oracle.com
Mon Jul 16 18:24:33 UTC 2018

Hi Tobias,

I think your suggestion should work. I'll need to think about how it might work when inlining across different class loaders. This could be tricky when LPoint; is a ValueType in CL1, but not a ValueType in CL2. I'll write a bunch of test cases to cover the scenarios.

Thanks

On 7/16/18 1:44 AM, Tobias Hartmann wrote:

Hi Ioi,

Inlining of a method 'callee' with a value type in it's signature into a method 'caller' is now only possible if the class declaring 'caller' has the value type in it's attribute. I think that's too strong because there can be very long inlining chains where task->method()->methodholder() is not aware of a value type being used deep inside that chain. I think we would need a check like this: If 'callee' has a (loaded) non-primitive type in its signature, check if that type is known to be a value type (Klass::isvalue()) and if so throw an ICCE if the 'callee' holder does not declare it in its value type attribute. That way we guarantee that assumptions of the caller at compile time (for example, non-nullness of the returned value type) are consistent with assumptions of the callee. It would be good to add the test(s) to the webrev. Thanks, Tobias On 14.07.2018 22:14, Ioi Lam wrote: http://cr.openjdk.java.net/~iklam/valhalla/8207219c2invokevtconsistency.v01/ https://bugs.openjdk.java.net/browse/JDK-8207219

This patch prevents improper inlining: when you have programs like this class VT { // knows that Point is a ValueType void crasher() { NonVT.foo(); } } class NonVT { // does NOT know that Point is a ValueType static Point x; static void foo() { x = bar(); // <-- cannot inline this call into VT.crasher } static Point bar() { return null; } } If we inlined the bar() call into VT.crasher, it would break JDK-8206140 [1], which assumes that a callee will never return a NULL value back to a compiled caller. Thanks - Ioi

[1] https://bugs.openjdk.java.net/browse/JDK-8206140 [lworld] Move return value null checks into the callee

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