The Possible(Expression|Statement) classes were added at
http://review.skia.org/375069. These classes were responsible for
capturing `__builtin_FILE()` and `__builtin_LINE()` when an
expression or statement was added to a hand-authored DSL program. This
allowed errors to be reported on the C++ file/line where they were
encountered. This was a good feature to have, when the plan was to
author the majority of SkSL code via DSL.
Later, IRNode positions were converted from an integer line number to
SkSL Positions at http://review.skia.org/518137. This gave us range
tracking, but at a high memory cost (16 bytes per IRNode, versus four
bytes when we tracked line numbers only).
Positions were reduced to 8 bytes at http://review.skia.org/521005 by
removing the filename, which was only used for hand-authored DSL. (The
size was pared all the way back to 4 bytes at
http://review.skia.org/533699 by packing the data more efficiently.)
__builtin_FILE/LINE capturing was removed entirely at
http://review.skia.org/528366; the filename was discarded anyway and
the line number didn't have a range and wasn't very meaningful without
a filename. Also, it didn't matter very much since we no longer intended
to hand-craft our programs in DSL.
At this stage, DSLPossibleExpression stopped adding value and simply
served to move Expressions around.
Change-Id: I29ac33e08dcc1804cc0619c1e8856ba28ebcc51d
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/542145
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
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