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Jake Bailey
89d9e33bca
* interp: bail out of loops that iterate too many times The existing loop guard (errLoopUnrolled) only fires when a loop body emits runtime instructions. Loops that are fully evaluable at compile time, such as inserting thousands of entries into a map, were not caught and could hang the compiler. Add a per-basic-block iteration counter that triggers a recoverable error (errLoopTooLong) when any block is entered more than 1000 times in a single function call. This defers the init function to runtime, which is the same behavior as other interp bailouts. Profiling showed that 83% of CPU time was spent in GC, caused by allocation pressure from the interp memory cloning on each map mutation. The iteration limit avoids this entirely by bailing out before the quadratic cost becomes significant. Performance on the reproducer from #2090 (map init with strconv.Itoa): entries before after 5,000 7.4s 2.1s 10,000 17.5s 2.1s 20,000 48.0s 2.8s 65,536 >180s (OOM) 3.2s * Add -interp-loop-limit