Optimal Basic Block Instruction Scheduling for Multiple-Issue Processors Using Constraint Programming

Instruction scheduling is one of the most important steps for improving the performance of object code produced by a compiler. A fundamental problem that arises in instruction scheduling is to find a minimum length schedule for a basic block--a straight-line sequence of code with a single entry point and a single exit point--subject to precedence, latency, and resource constraints. Solving the problem exactly is NPcomplete, and heuristic approaches are currently used in most compilers. In contrast, we present a scheduler that finds provably optimal schedules for basic blocks using techniques from constraint programming. In developing our optimal scheduler, the keys to scaling up to large, real problems were improvements to the constraint model and to the constraint propagation phases. We experimentally evaluated our optimal scheduler on the SPEC 2000 integer and floating point benchmarks. On this benchmark suite, the optimal scheduler was very robust and scaled to the largest basic bl...

• Type: Journal
• Year: 2008
• Where: IJAIT
• Authors: Abid M. Malik, Jim McInnes, Peter van Beek
• Keywords: Basic Blocks, IJAIT 2008, Instruction Scheduling, Optimal Scheduler