Implement Generational Garbage Collection

Generational Hypothesis

Most objects die young. Split heap into young (nursery) and old generations. Minor collections copy survivors with copying GC; promote long-lived objects to old gen. Major collections run rarely. HotSpot's G1 and .NET GC extend this model.

Minor vs Major

Allocate in nursery until full. Minor GC copies survivors to survivor space or promotes. Old gen collected less often with mark-sweep or mark-compact.

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• Write barriers record old->young pointers
• Promotion threshold: survive N minor collections
• Card tables summarize dirty old-gen cards
• Tuning nursery size trades frequency vs pause

Connecting to real compilers

Production compilers embed this step inside a longer pipeline. GCC flows through cpp, cc1, assembly, and ld; Clang uses the driver, Sema, LLVM IR passes, and a target backend. LLVM bitcode, JVM bytecode, and WASM are other familiar IRs at the same layer. The exercise isolates one pass so you can test it alone before chaining it to the next stage.

Why for this exercise

You will implement generational garbage collection with nursery and old generation. This exercise requires a fast minor collection, promotion policy, and write barriers for cross-generation pointers.