tree 4b71a32c45849913d7e63b20ef062fcac951dbc7
parent 496fd46214cdd12dd56ae936d6ccb8a65116675d
author David 'Digit' Turner <digit@google.com> 1649854190 +0200
committer Commit Bot <commit-bot@chromium.org> 1650041849 +0000

Add ResolvedTargetData class

This class re-implements some of the expensive recursive computations
over the build graph that are currently implemented in
Target::OnResolved(). This will allow, in a future CL, to move these
computations out of the graph builder, that runs exclusively on the
main thread, and into parallel worked pool threads.

Another benefit is that the computations are performed top-down
(i.e. by recursing from dependents to dependencies), which limits
them to only the targets that actually need them. By contrast, the
current code propagates values from dependencies to dependents
unconditionally, resulting in un-necessary work and data associated
for _every_ target in the graph.

To avoid duplicate work, each ResolvedTargetData call does record or
reuses intermediate target-specific values. This will be leveraged,
in yet another future CL, by setting up and using one
ResolvedTargetData instance per worker pool thread.

Future CLs will update the Ninja target writers to use instances of
this class, and remove the Target methods that return the same results.

+ Add TargetPublicPair to model a compact (target_ptr, is_public_flag)
  pair, and TargetPublicPairListBuilder to generate lists of such
  instances efficiently.

+ Add ResolvedTargetDeps which provides a compact iterator over
  different sets of target dependencies, since profiling shows
  that using a DepsIterator instance is much slower during
  graph-traversal heavy operations.

Both classes are used internally by ResolvedTargetData.

Bug: None
Change-Id: I83f2e3aed83e0ac1b96bb887e7f3f3f9a01a7156
Reviewed-on: https://gn-review.googlesource.com/c/gn/+/13624
Reviewed-by: Sylvain Defresne <sdefresne@chromium.org>
Commit-Queue: David Turner <digit@google.com>