LIR: Low-Level Intermediate Representation

LIR stands for “Low-Level Intermediate Representation”

Differences between HIR and LIR:

A valid LIR program is a valid HIR program that in addition verifies the following constraints:

• No nested seq:

  The HIR tree must be flattened in a single thread of execution. Therefore, there must be at most one seq per function.

• No eseq:

  Similarly, the instruction eseq must not be used.

• No nested call:

  Calls cannot be embedded within other calls. Actually, the restriction is even stronger than this: a call can only appear in the following patterns:

  move dest call ...

  A function call.

  sxp call ...

  A procedure call.

• One way cjump:

  cjumps must be normalized in such a way that they are always followed by their negative destination.