<regex>: Simplify unwinding
#5961
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StephanTLavavej
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enhancement
StephanTLavavej
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Jan 5, 2026
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I'm mirroring this to the MSVC-internal repo - please notify me if any further changes are pushed. |
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Following #5828 and #5835, general stack unwinding is skipped when a regex (or an asserted pattern) matches successfully and matching does not follow the leftmost-longest rule. As a consequence, conditions based on
_Failedor_Longestin the general unwinding loop have become superfluous, since they are always true. (For some opcodes, only_Failedwas tested, but this was because they could not be generated in leftmost-longest mode.)This removes all of these unnecessary conditions, replacing them by an initial assert to check that
_Failed || _Longestis always true. Subsequently, we can use the same handler for_After_assertand_Do_nothingbecause no work is performed when backtracking over them. Similarly, the handler for_Disjunction_eval_alt_on_failurewould immediately fall through to the handler of_Disjunction_eval_alt_always, so we can just fuse these two opcodes.