Why SSA?
a day ago
- #SSA
- #compilers
- #optimization
- SSA (Static Single Assignment) is a popular compiler architecture used in optimizing compilers like LLVM, GCC, Go, CUDA, Swift, and MSVC.
- SSA simplifies program analysis and transformation by ensuring each variable is assigned only once, making the program resemble a combinatorial circuit.
- Basic blocks in SSA form are sequences of non-control flow operations ending with a terminator, forming a Control Flow Graph (CFG).
- Dominance relations in CFGs help in structuring and optimizing the program by defining hierarchical relationships between blocks.
- Memory dependency analysis is crucial for lifting loads and stores out of memory, optimizing performance by reducing redundant operations.
- SSA's circuital nature allows for efficient graph-based algorithms, simplifying optimizations like dead code elimination and CFG simplification.
- Cleanup passes, such as unused result elimination and CFG simplification, help maintain an efficient and readable IR after transformations.
- Future topics in SSA optimization include CSE/GVN, loop optimizations, and transitioning from SSA to finite-register machine code.