Representing local variables in compiler IRs

It's useful to lift local variables into SSA nodes in a compiler

But local variables can be observed/reified by explicit runtime reflection (incl. locals(), eval(), ...), exceptions, debuggers

Local variables also have nonlocal things sometimes like Ruby blocks

LLVM

• CFG
• Allocate everything on stack
• mem2reg

PyPy

• Trace

JavaScriptCore

Cinder

• FrameState
• Ignore locals()/sys._getframe

ZJIT

Graal

• FrameState