• Hot-spot compilation: identify code paths of most use, slowly compile those to efficient code, and run everything else in a much slower interpreter.
• Exupery is designed to work along the interpreter and take effect in specific cases where Smalltalk's dynamism is not required.
• Tree based optimizations
• Coloring coalescing register allocator
• Temporaries were still kept on the stack because only arithmetic operations benefitted from registerization.
• Inspiration from Self; using type introspection to generate better code or something.
• Self-hosted in the image so Smalltalkers can modify it.

Issues with Squeak

• Integer tags may require clearing the tag, doing an operation, and restoring the tag.
• Performance issues with how objects are marked across generations.