[swift-dev] Having 64-bit swift_retain/release ignore all negative pointer values
jgroff at apple.com
Tue Mar 1 15:33:59 CST 2016
In swift_retain/release, we have an early-exit check to pass through a nil pointer. Since we're already burning branch, I'm thinking we could pass through not only zero but negative pointer values too on 64-bit systems, since negative pointers are never valid userspace pointers on our 64-bit targets. This would give us room for tagged-pointer-like optimizations, for instance to avoid allocations for tiny closure contexts.
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