Emit traps for unreachable nodes #41465
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Raw `unreachable` in LLVM is somewhat dangerous since LLVM will literally stop emitting code there, so if the unreachable is wrong, execution will crash into whatever subsequent code exists, causing strange and mysterious errors and incorrect backtraces that are hard to debug without rr. As a result, we basically always emit a safety trap call before an `unreachable` terminator, which will abort execution at the point where unreachable was executed and at least provide proper backtraces. However, we neglected to do this for literal unreachables that came from Julia IR (i.e. ReturnNodes with undef val field). Fix that to make debugging easier if unreachable ever gets accidentally executed.
vtjnash
reviewed
Jul 5, 2021
vtjnash
approved these changes
Jul 5, 2021
Co-authored-by: Jameson Nash <vtjnash@gmail.com>
JeffBezanson
approved these changes
Jul 6, 2021
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Raw
unreachablein LLVM is somewhat dangerous since LLVM will literallystop emitting code there, so if the unreachable is wrong, execution will
crash into whatever subsequent code exists, causing strange and mysterious
errors and incorrect backtraces that are hard to debug without rr. As a
result, we basically always emit a safety trap call before an
unreachableterminator, which will abort execution at the point where unreachable was
executed and at least provide proper backtraces. However, we neglected
to do this for literal unreachables that came from Julia IR (i.e. ReturnNodes
with undef val field). Fix that to make debugging easier if unreachable
ever gets accidentally executed.