Local Code Generation and Compaction in Optimizing Microcode Compilers.

摘要

Horizontal micro-architectures often have features that make it difficult for a compiler to produce good object code from a high-level language. Although the problem of compacting microcode into a near-minimal number of microinstructions has received a great deal of attention, other phases of the compiler have not been studied as thoroughly. This dissertation explores methods of generating quality microcode for horizontal microarchitectures, compacting the microcode, and the interaction between code generation and compaction. There are often several code sequences that perform the same computation for a given micro-architecture. If the code generation and compaction phases of the compiler are executed sequentially, the code generator may not be able to determine the best code, because a code sequence that compacts well in one situation may contain several bottlenecks in another. This dissertation explores three methods of coupling the code generation and compaction phases of the compiler, and concludes that subtle micromachine features make it very difficult to produce good code unless the code generator actually produces several candidate code sequences that are compacted and compared with one another.