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Master the fundamental concepts of optimizations through this focused micro-challenge.
Peephole optimization slides a small window over instructions and replaces matching patterns with cheaper equivalents. GCC's peephole2 pass and LLVM's machine peephole delete mov r, r, fuse compare-branch, and swap redundant loads.
jmp L; L: eliminates the jump. add r, 0 deletes the add. mov r1, X; mov r2, r1 may become one move if safe.
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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.
You will implement peephole optimizations on your instruction list. This exercise asks you to define local patterns and rewrite sequences that are redundant or substitutable with fewer instructions.
Implement a peephole optimizer for x86 assembly or TAC.
Implement pattern matching for:
Create a pattern database:
Handle these specific patterns (minimum):
mov X, X → removeadd X, 0 → removemul X, 1 → removemul X, 0 → mov X, 0mul X, 2^n → shl X, njmp L; L: → remove jumpRun until fixed point (no more matches)
Three hints are available for this task, revealed one at a time inside the code workspace so you can struggle productively before seeing them.
All starter code and reference implementations are available for your local setup.
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