8354323: Safeguard SwitchBootstraps.typeSwitch when used outside the compiler

[biboudis]

While the compiler does not allow invalid queries to flow into SwitchBootstraps:typeSwitch, a library user could do that and typeSwitch does not prevent such usage pattern errors resulting in erroneous evaluation.

For example this is not valid Java (and protected) by javac:

byte b = 1;
switch (b) {
    case String s -> System.out.println("How did we get here? byte is " + s.getClass());
}

but this is a valid call (and not protected):

CallSite shortSwitch = SwitchBootstraps.typeSwitch(
    MethodHandles.lookup(), 
    "", 
    MethodType.methodType(int.class, short.class, int.class),  // models (short, int) -> int
    String.class);

The SwitchBootstraps.typeSwitch returns wrong result since the code was reasoning erroneously that this pair was unconditionally exact.

This PR proposes to add the safety check in unconditional exactness which will return false in erroneous pairs and then the actual check will be delegated to instanceof. For the case of erroneous pairs with primitive booleans there is a check in the beginning of the type switch skeleton.

---

Progress

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Issue

• JDK-8354323: Safeguard SwitchBootstraps.typeSwitch when used outside the compiler (Bug - P4)

Reviewers

• Chen Liang (@liach - Reviewer)

Reviewing

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@biboudis This change now passes all automated pre-integration checks.

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8354323: Safeguard SwitchBootstraps.typeSwitch when used outside the compiler

Reviewed-by: liach

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At the time when this comment was updated there had been 90 new commits pushed to the master branch:

• 8c1b915: 8356126: Duplication handling and optimization of CaptureCallState
• 3f6b177: 8332934: Do loop with continue with subsequent switch leads to incorrect stack maps
• cb02158: 8354461: Update tests to disable streaming output for attach tools
• ... and 87 more: https://git.openjdk.org/jdk/compare/995d54161fed657f38753813f55d0591e77a42e3...master

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[mlbridge]

Webrevs

• 00: Full (835fb6ab)

[liach]

Can we merge this into isNotValidPair(...) || unconditionalExactnessCheck(...) then do nothing? The next label is already in theory immediately bound to the instruction after goto.

[biboudis]

The empty body means that we unconditionally return the index case 0 -> /*no if is generated*/ return 0;.

I confirmed that by merging, the following test would not pass. It returns erroneously 0, instead of 1.

testPrimitiveType((byte) 1, byte.class,0, 1, boolean.class, byte.class);

[liach]

looks good!