tree 9c0d9899dc112ff93a802d7d426fef872d7deab6
parent 395b48825aa294b0934ef302c039b0ba45ccf2d0
author Ben Clayton <bclayton@google.com> 1618605021 +0000
committer Commit Bot service account <commit-bot@chromium.org> 1618605021 +0000

Add ShareableCloneable, dervies from Cloneable

The CloneContext will currently de-duplicate any pointers that are cloned multiple times, however this isn't ideal behavior for AST nodes.

AST nodes must be unique in the tree, so a non-transform clone of the AST from one program to another should only ever Clone() called once per node. Hitting the map for these is inefficent, worse still, there are cases in the transforms where we actually *want* to create N copies of the same source node. The current implementation makes this impossible.

This change introduces ShareableCloneable, a new base class that derives from Cloneable.
Repeated calls to CloneContext::Clone() for Cloneable pointer types will now produce a new, unique instance per call.

Repeated calls to CloneContext::Clone() for ShareableCloneable pointer types will de-duplicate as before.

type::Type objects are shared, want deduplication while cloning, so now derive from ShareableCloneable.
ast::Node continues to derive from Cloneable.

Bug tint:469

Change-Id: I5ca906d507de6271d5d715cfdc962a55b721e821
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/47776
Commit-Queue: Ben Clayton <bclayton@google.com>
Reviewed-by: Antonio Maiorano <amaiorano@google.com>
Reviewed-by: James Price <jrprice@google.com>