chapter3-m1-ziavras

Use the same reg or memory location called a name but

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: e reg. names are fixed) • Difficult with memory locations (because 2+ addresses may refer to same location & be different) S. Ziavras Name Dependence • • Definition: 2 instrs. use the same reg. or memory location, called a name, but there is no flow of data between the instrs. associated with that name th th 2 types of name dependences between an instr. i that precedes that precedes instruction j in program order: program order: – Antidependence: j writes a reg. or memory location that i reads – Output dependence: i & j write the same reg. or memory location SOLUTION SOLUTION • REGISTER RENAMING can remove name dependences S. Ziavras Unknown Dependence • Dependence relation between 2 instrs. cannot be determined in the following situations: – Subscript of variable is itself subscribed (indirect addressing) – Subscript doesn’t contain loop index variable – Variable appears more than once with subscripts having different coefficients of loop variable – Subscript is nonlinear in loop index variable S. Ziavras Dependence Graphs • Nodes: instructions • Data dependence: i j • Name dependence dependence – Antidependence: i j – Output dependence: i S. Ziavras j Dependence...
View Full Document

This document was uploaded on 02/09/2014.

Ask a homework question - tutors are online