Remove MemberName Object Ref from Stack in OpenJDK MethodHandle linkTo* INL Methods #22112
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The JIT needs to pass in a MemberName object when calling the various linkTo* INL methods in the OpenJDK MethodHandle implementation. The MN is only used by the INL to extract the target method, and then is no longer needed, so the INL moves the MN from _sp[0] to _sp[methodArgCount] (the arg count of the target method). This creates issues on x86 32bit when the target is compiled upon invocation from linkTo*. If the target gets compiled, the call-cleanup for j2iTransition will get skipped and we only remove the target method's arguments and not the MN. So, the MN is still on the stack when we return from the target, and eventuallly the MN address ends up in the pc. Fixes: eclipse-openj9#18751 This commit removes the MN from the stack before calling the target in the linkTo* methods. Signed-off-by: Matthew Hall <matthew.hall3@outlook.com>
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When calling the various linkTo methods (namely
linkToStatic(),linkToSpecial(),linkToVirtual(),linkToInterface()), the JIT must pass in aMemberNameobject whichlinkTo*()expects to be at_sp[0]. ThelinkTo*()methods use the MN to find the target method, after which it is not needed. So, before running the target, we move the MN to_sp[methodArgCount], wheremethodArgCountis the argument count of the target method.This creates problems on x86, where we pass arguments on the stack. For cases where the target is not compiled, we must transition into the VM to link using one of the
linkTo*()methods (as opposed to running usingdispatch*()directly from the JIT'ed code). But if the invocation in the VM triggers a recompilation, only the arguments of the target are popped before returning, and not the MN . This means the MN will still be on the stack upon return from the target, and eventually ends up in the pc since the arguments to the helper are assumed to have been cleaned up.For the case where the target is still interpreted, we still only pop target's args before returning to the JIT and again the MN is still on the stack.
This PR changes the
linkTo*()methods to pop the MN from the stack as it is not used by the target.#18751