Register allocation via graph coloring
Register allocation via graph coloring
Improvements to graph coloring register allocation
ACM Transactions on Programming Languages and Systems (TOPLAS)
ACM Transactions on Programming Languages and Systems (TOPLAS)
Modern compiler implementation in Java
Modern compiler implementation in Java
Using node merging to enhance graph coloring
Proceedings of the ACM SIGPLAN 1999 conference on Programming language design and implementation
Register allocation & spilling via graph coloring
SIGPLAN '82 Proceedings of the 1982 SIGPLAN symposium on Compiler construction
Optimistic Register Coalescing
PACT '98 Proceedings of the 1998 International Conference on Parallel Architectures and Compilation Techniques
An optimistic and conservative register assignment heuristic for chordal graphs
CASES '07 Proceedings of the 2007 international conference on Compilers, architecture, and synthesis for embedded systems
Coloring-based coalescing for graph coloring register allocation
Proceedings of the 8th annual IEEE/ACM international symposium on Code generation and optimization
| Hi-index | 0.00 |
Graph-coloring register allocators can eliminate copy instructions from a program by coalescing the interference graph nodes corresponding to the source and destination. Briggs showed that by limiting coalescing to those situations that he dubbed “conservative,” it could be prevented from causing spilling, that is, a situation where the allocator fails to assign a register to each live range. George and Appel adopted Briggs's conservativeness criterion in general, but provided an alternative criterion (the George test) to use in those cases where one of the nodes has been “precolored,” that is, preassigned a specific register. They motivated this alternative criterion by efficiency considerations, and provided no indication of the relative power of the two criteria. Thus it remained an open question whether the efficiency had been bought at the expense of reduced coalescing. Their implementation also used a limited version of the Briggs test, in place of the original, full version, without any comment on the impact of this substitution. In this article, we also present an analogously limited version of the George test.Thus we are now confronted with four different criteria for conservative coalescing: the full and limited Briggs tests and the full and limited George tests. We present a number of theorems characterizing the relative power of these different criteria, and a number of theorems characterizing the form of safety that each achieves. For example, we show that for coalescing with precolored nodes, the full George criterion is strictly more powerful than the full Briggs criterion, while offering an equally strong safety guarantee. Thus no coalesces are lost through George and Appel's introduction of the George test, and some can be gained without sacrificing safety.We also show that George and Appel's limited version of the Briggs test is probably undesirable. Although a slightly stronger safety result applies to it than to the full Briggs test, this comes at the expense of eliminating all coalesces that can reduce spilling.