Bug 604426 adds an analysis for determining which locals are defined at each point in a script, and whether a local is ever used before it is defined. This approximates liveness information (see bug 604426 comment 7), which the tracer can use when capturing types at the head of a loop and more robustly deal with loops that contain temporaries.
Created attachment 483654 [details] [diff] [review] WIP This patch works on the V8 tests (includes the analysis from bug 604426, since that hasn't landed yet). For pure TM on v8-v5, I get these times: crypto 334ms -> 312ms delta-blue 410ms -> 274ms raytrace 617ms -> 736ms (need to figure this one out) With -m -j all three slow down (need to figure these out too).
Obsolete with the removal of tracejit.