Itanium processors execute instructions in bundles. A bundle contains up to three instructions, and an associated template. The template defines which type of execution unit processes each instruction in the bundle.
IAS enables several levels of bundle definition:
Explicit bundling and template definition. You define the bundle boundaries and the bundle template.
Explicit bundling without template definition. You define the bundle boundaries; IAS chooses the best fitting bundle template.
Implicit bundling. IAS chooses bundle boundaries and the bundle template by selecting the optimal code size arrangements.
At all the bundle definition levels IAS inserts required NOPs.
The bundling feature is fully defined in the IntelŪ ItaniumŪ Architecture Assembly Language Reference Guide.