Running the attached testcase in an opt tip tracemonkey shell on Mac, I get the following for "Elapsed time": interp: 563 -j: 248 -m: 300 -j -m: 321 Looking at TMFLAGS=aborts,stats it looks like this for -j: Abort recording of tree /Users/bzbarsky/bar.js:157@45 at /Users/bzbarsky/bar.js:8@87: No compatible inner tree. recorder: started(10), aborted(1), completed(11), different header(0), trees trashed(9), slot promoted(0), unstable loop variable(3), breaks(0), returns(0), merged loop exits(2), unstableInnerCalls(1), blacklisted(0) monitor: exits(40), timeouts(1), type mismatch(0), triggered(41), global mismatch(0), flushed(0) and like this for -j -m: Abort recording of tree /Users/bzbarsky/bar.js:157@45 at /Users/bzbarsky/bar.js:8@87: No compatible inner tree. Abort recording of tree /Users/bzbarsky/bar.js:157@45 at /Users/bzbarsky/bar.js:8@87: No compatible inner tree. Abort recording of tree /Users/bzbarsky/bar.js:157@45 at /Users/bzbarsky/bar.js:8@87: Inner tree is trying to stabilize, abort outer recording. Abort recording of tree /Users/bzbarsky/bar.js:157@45 at /Users/bzbarsky/bar.js:8@87: Inner tree is trying to stabilize, abort outer recording. Abort recording of tree /Users/bzbarsky/bar.js:157@45 at /Users/bzbarsky/bar.js:8@87: Inner tree is trying to stabilize, abort outer recording. recorder: started(10), aborted(5), completed(6), different header(0), trees trashed(5), slot promoted(0), unstable loop variable(2), breaks(0), returns(0), merged loop exits(1), unstableInnerCalls(2), blacklisted(2) monitor: exits(10006), timeouts(0), type mismatch(0), triggered(10006), global mismatch(0), flushed(0) Note the larger number of aborts + blacklists and the _way_ larger number of triggered+exits that ensues. Marking dependent on bug 580468 for now.

Is there a missing attachment?

Gack. I thought I'd attached it here. Coming up.

Interp: 1071 TM: 1086 JM: 396 JM+TI: 211 d8: 112 JM+TI is definitely better than plain JM, but v8 is still 2x faster.