gh-104584: Fix error handling from backedge optimization #106484
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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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When
_PyOptimizer_BackEdgereturnsNULL, we should restorenext_instr(andstack_pointer). To accomplish this we should jump toresume_with_errorinstead of justerror.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
disoutput.