JSStackFrame Evisceration
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This leaves sizeof(JSStackFrame) == 10 words (11 on 32-bit), but we only need to initialize 4 of those words on the common call path; the rest can be lazily (or never) initialized.
Members to remove
Sorted in estimated order of benefit / difficulty:
| Task | Size (wks) | Assignee | Note |
| Xargc/argv/fun/script/thisv | 3 | lw | Requires StackSegment changes. |
| Xncode | 3 | Merge it with savedPC in method-jit. Requires building map HW PC --> bytecode (which we sortof already heave | |
| scopeChain | .5 | ||
| XdisplaySave | 1 | cdleary | Remove display optimization for great justice! |
| XhookData | .1 | lw | Lazily initialize using JSStackFrame::flags. Included in bug 539144. |
| Xannotation | 3 | sayrer | Trivial if we can remove callers in nsScriptSecurityManager. Alas, that is not trivial, so this is going to take a while. For now, we lazily initialize which gives practically all the benefit. |
| XcallerVersion | .5 | cdleary | Mostly the challenge is just understanding the actual use case. |
| XblockChain | 1 | wmmcloskey | A bit tricky |
| rval | 1 | Lazily initialize with a JSStackFrame::flags bit and avoid ever writing in the hot JM call/return paths. | |
| Ximacpc | 1 | cdleary | Leave uninitialized in call path and use JSStackFrame::flags to indicate whether there is or is not an imacpc. |