Associative Instruction Reordering to Alleviate Register Pressure

International audienceRegister allocation is generally considered a practically solved problem. For most applications, the register allocation strategies in production compilers are very effective in controlling the number of loads/stores and register spills. However, existing register allocation strategies are not effective and result in excessive register spilling for computation patterns with a high degree of many-to-many data reuse, e.g., high-order stencils and tensor contractions. We develop a source-to-source instruction reordering strategy that exploits the flexibility of reordering associative operations to alleviate register pressure. The developed transformation module implements an adaptable strategy that can appropriately control the degree of instruction-level parallelism, while relieving register pressure. The effectiveness of the approach is demonstrated through experimental results using multiple production compilers (GCC, Clang/LLVM) and target platforms (Intel Xeon Phi, and Intel x86 multi-core)

Combined instruction scheduling and register allocation

Master'sMASTER OF SCIENC

Survey on Instruction Selection: An Extensive and Modern Literature Review

Instruction selection is one of three optimisation problems involved in the code generator backend of a compiler. The instruction selector is responsible of transforming an input program from its target-independent representation into a target-specific form by making best use of the available machine instructions. Hence instruction selection is a crucial part of efficient code generation. Despite on-going research since the late 1960s, the last, comprehensive survey on the field was written more than 30 years ago. As new approaches and techniques have appeared since its publication, this brings forth a need for a new, up-to-date review of the current body of literature. This report addresses that need by performing an extensive review and categorisation of existing research. The report therefore supersedes and extends the previous surveys, and also attempts to identify where future research should be directed.Comment: Major changes: - Merged simulation chapter with macro expansion chapter - Addressed misunderstandings of several approaches - Completely rewrote many parts of the chapters; strengthened the discussion of many approaches - Revised the drawing of all trees and graphs to put the root at the top instead of at the bottom - Added appendix for listing the approaches in a table See doc for more inf