[release/9.0-staging] JIT: Include more edges in BlockDominancePreds to avoid a JIT crash
#110568
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Because of spurious flow it is possible that the preds of the try-begin block are not the only blocks that can dominate a handler. We handled this possibility, but only for finally/fault blocks that can directly have these edges. However, even other handler blocks can be reachable through spurious paths that involves finally/fault blocks, and in these cases returning the preds of the try-begin block is not enough to compute the right dominator statically.
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BlockDominancePredsBlockDominancePreds to avoid a JIT crash
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Backport of #110531 to release/9.0-staging
/cc @jakobbotsch
Customer Impact
Certain patterns of exception handling (involving nested filters, try-finally and try-catch) can cause the JIT to crash when the method is jitted with optimizations enabled. Reported by customer in #109981.
The problem occurs when:
See the added test case for a C# example.
In this case the JIT computes a wrong dominator block for the catch-handler (2), which later causes a null pointer dereference.
Regression
The issue was introduced in #94672.
Testing
Added a test case that hits the crash without the fix. Also verified the fix on the customer's test case.
Risk
Low.