Bug 125425 – Fold storage pointer for GC-allocated typed arrays

• Status: REOPENED
• Component: JavaScriptCore

[Filip Pizlo]

This probably won't be *too* profitable but I suspect that eventually it'll be needed.

[Filip Pizlo]

*** This bug has been marked as a duplicate of bug 161100 ***

[Filip Pizlo]

Nope, this is still a bug.

Even if the GC-allocated typed array doesn't move, we still can't constant-fold pointers to it because of neutering:

- To constant-fold, we need to install a watchpoint on the typed array's underlying buffer to make sure that we get notified if it gets neutered.
- To install a watchpoint, we need to request the buffer.
- To request the buffer, we need to move the backing store out of GC space.
- To move it out of GC space, we need to malloc a new backing store and copy the data over and repoint m_vector.
- Therefore, constant folding will fold to the *old* buffer.

Ouch!