gh-104584: Fix error handling from backedge optimization - #106484
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gvanrossum merged 3 commits intoJul 6, 2023
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This fixes a nasty bug in exception handling. Apparently some part of the computation that determines where the exception handler is uses next_instr, which was pointing at the JUMP_BACKWARD instruction instead of where the error was occurring. Better fix for _PyOptimizer_BackEdge error handling
Offsets in debug output identifying the start of the trace are now measured in bytes (and the text shows it).
markshannon
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Jul 6, 2023
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One minor issue, otherwise LGTM
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Python/optimizer.c
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When _PyOptimizer_BackEdge returns NULL, we should restore next_instr (and stack_pointer). To accomplish this we should jump to resume_with_error instead of just error.
The problem this causes is subtle -- the only repro I have is in PR gh-106393, at commit d7df54b. But the fix is real (as shown there).
While we're at it, also improve the debug output: the offsets at which traces are identified are now measured in bytes, and always show the start offset. This makes it easier to correlate executor calls with optimizer calls, and either with dis output.