SSA Destruction for Machine Code

• Published in: SSA-based Compiler Design pp. 285 - 302
• Main Author: Rastello, Fabrice
• Format: Book Chapter
• Language: English
• Published: Cham Springer International Publishing 2022
• Subjects: Aggressive coalescing; Application binary interface (ABI); Branch instruction problem; Calling conventions; Code generation; Compiler back-end; Compiler design; Conservative coalescing; Conventional SSA (C-SSA); Copy insertion; Copy mode; Critical edge; Dead code elimination; Dedicated register; Duplicated edge problem; Edge splitting; Global value numbering (GVN); Instruction set architecture (ISA); Interference; Interference check; Isolation of phi-nodes; Just-in-time compiler (JIT); Liveness check; Lost-copy problem; Machine level; Multiplexing mode; Parallel copy; Phi-web; Pinning; SSA destruction; Static single assignment form (SSA form); Swap problem; Two-address mode; Value-based interference
• ISBN: 303080514X; 9783030805142
• DOI: 10.1007/978-3-030-80515-9_21

Chapter 3 of this book provides a basic algorithm for destructing SSA that suffers from several limitations and drawbacks: First, it works under implicit assumptions that are not necessarily fulfiled at machine level; second, it must rely on subsequent phases to remove the numerous copy operations it inserts; finally, it subsequently increases the size of the intermediate representation, thus making it unsuitable for just-in-time compilation. The current chapter addresses these three issues: correctness (handling of machine-level constraints), code quality (elimination of copies), and algorithm efficiency (speed and memory footprint). The layout falls into three corresponding sections.