These are two bits of data stored in a script's analysis info and used during Ion compilation. If the script has not been analyzed before Ion compilation, as is the case post bug 865059, the bits are not accumulated and the generated code is worse. This is the cause of the dromaeo DOM/CSS regressions post bug 865059. The attached patch allows this data to also be accumulated on a BaselineScript's ICs, and fixes the above regressions (https://tbpl.mozilla.org/?tree=Try&rev=3525a04167a6).

Comment on attachment 746676 [details] [diff] [review] patch Review of attachment 746676 [details] [diff] [review]: ----------------------------------------------------------------- Nice.

The Dromaeo DOM and Dromaeo CSS regressions appear to be completely fixed; in most cases the performance is now *better* than it was pre bug 865059: https://groups.google.com/d/topic/mozilla.dev.tree-management/UZ7oRo6324M/discussion Original thread for reference: https://groups.google.com/d/topic/mozilla.dev.tree-management/qJ4I0j0CKTI/discussion