1023078 - PJS: Type inference weakness (?) causes bailout from parallel section

Status: RESOLVED WONTFIX

(Core :: JavaScript Engine, defect)

Description

[Lars T Hansen [:lth]]

Attachment: ray-pjs-tile.js

Consider the attached ray tracer (not very small, sorry).  If the two calls to the function "obscure" are left commented-out as in the sample then this program will repeatedly bail out from the parallel section with an "unsupported operation" failure.  If the two calls are in place, the program enters the PJS engine and stays there reliably.

I haven't tracked down the root cause but it seems plausible that type information computed for the objects that are returned is not stable, or that it is computed in such a way that run-time variations cause a bailout.  Notably, the "intersect" method will return objects whose "obj" field can be null or one of several known types.  By calling "obscure" on the value stored in obj, the type is laundered to Object.