1264997 - JSOP_LABEL's offset should be a source note.

Status: RESOLVED INVALID

(Core :: JavaScript Engine, defect)

Description

[Nicolas B. Pierron [:nbp]]

Currently IsJumpOpcode encode a special case for JSOP_LABEL, this special case is a work-around made to account the fact that we have an offset as argument of JSOP_LABEL.

The only code which relies on this offset is in IonBuilder, and it has no purpose for the execution.  We should move it as a source-note information in a similar way as we do for loops.

Comment 1

[Jan de Mooij [:jandem]]

As far as I know, we prefer bytecode operands over source notes.

Source notes require an extra lookup and it'd be nice to remove them altogether at some point (and use a more efficient system for lineno/column information).

Comment 2

[Nicolas B. Pierron [:nbp]]

My understanding was that if we do not need it for the execution, we should move it to the source notes.

Comment 3

[Jan de Mooij [:jandem]]

(In reply to Nicolas B. Pierron [:nbp] from comment #2)
> My understanding was that if we do not need it for the execution, we should
> move it to the source notes.

I think, for the most part, source notes are a leftover from the old decompiler. Looking up source notes for a particular pc is very inefficient (see GSNCache) and I'd love to kill them entirely at some point.

Comment 4

[Jan de Mooij [:jandem]]

(I don't really care about making this one a source note though, JSOP_LABEL isn't that common. It'd be nice to avoid the source note overhead for the more common ops though.)

Comment 5

[Jason Orendorff [:jorendorff]]

(In reply to Jan de Mooij [:jandem] from comment #3)
> I think, for the most part, source notes are a leftover from the old
> decompiler. Looking up source notes for a particular pc is very inefficient
> (see GSNCache) and I'd love to kill them entirely at some point.

Yes. I'd like to kill them off for everything except location information (which I think has to be inconveniently compressed, by default at least, to avoid bloat).