Optimal instruction scheduling using integer programming

{ This paper presents a new approach to local instruction scheduling based on integer programming that produces optimal instruction schedules in a reasonable time, even for very large basic blocks. The new approach rst uses a set of graph transformations to simplify the datadependency graph while preserving the optimality of the nal schedule. The simpli ed graph results in a simpli ed integer program which can be solved much faster. A new integerprogramming formulation is then applied to the simpli ed graph. Various techniques are used to simplify the formulation, resulting in fewer integer-program variables, fewer integer-program constraints and fewer terms in some of the remaining constraints, thus reducing integer-program solution time. The new formulation also uses certain adaptively added constraints (cuts) to reduce solution time. The proposed optimal instruction scheduler is built within the Gnu Compiler Collection (GCC) and is evaluated experimentally using the SPEC95 oating po...

• Type: Conference
• Year: 2000
• Where: PLDI
• Authors: Kent D. Wilken, Jack Liu, Mark Heffernan
• Keywords: Basic Blocks, Optimal Instruction, PLDI 2000, Programming Languages, Simpli Ed Graph