[PATCH] D16569: Emit line 0 line information for interesting 'orphan' instructions

David Blaikie via llvm-commits llvm-commits at lists.llvm.org
Wed Jan 27 10:09:26 PST 2016

On Wed, Jan 27, 2016 at 10:06 AM, Paul Robinson via llvm-commits <
llvm-commits at lists.llvm.org> wrote:

> probinson added a comment.
> In http://reviews.llvm.org/D16569#337412, @probinson wrote:
> > Second, I'd hope that the column number is irrelevant and so we
> shouldn't bother explicitly setting it to zero. That's probably something
> that would have to be handled where the line-table gets encoded, rather
> than here, and so can be deferred to a follow-up.
> To quantify this, a quick experiment showed a line-0 directive occupied 5
> bytes, of which 2 bytes were setting the column to zero.  Not setting the
> column reduces the size increase by 40%.

Good to know - does that include changing the file too? (On either side of
the equation/data)
Though I expect some of the cost of these new line table entries includes
changing it back to something else on the other side - in some cases I
imagine it'll be changing it back to the same file/line, potentially.
Though I suppose if we don't change the file, we'll save both the change,
and the change back. Column probably changes anyway so it doesn't cost us
anything on the change "back" perhaps.

- Dave

> http://reviews.llvm.org/D16569
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