Checkpoint Map
A checkpoint map is an optional field of the ILA refinement map that specifies when the architectural variables (AVs) of the instruction-level architecture (ILA) model should be compared against the corresponding RTL architectural variables (RTAVs) of the RTL executable model (RTEM) during tandem simulation.
Origin and Context
The checkpoint map is one of two optional fields added to the original ILA refinement map (introduced in formal verification work for processors and accelerators) to support the generalized tandem simulation methodology. As stated in the source: "(iv) Checkpoint map and (v) 'cold start' map: are not part of the original ILA refinement map [8] and have been added as part of this work to support tandem simulation."
Position Within the Refinement Map
The refinement map defines two main fields — the AV map (specifying what to check, i.e., the correspondence between ILAVs and RTAVs) and the instruction map (specifying instruction start/finish boundaries in the RTL implementation). It additionally supports three optional fields: the interface map, the checkpoint map, and the "cold start" map.
Three Types of Checkpoints
The methodology augments the refinement map with the checkpoint map to support the following three types of checkpoints, used in Scenario 2 of tandem simulation (periodic checking of AVs):
- Checkpoint period (P) — invokes checking for every P instructions.
- Checkpoint sequence ([t1, t2, ...]) — invokes checking at the n-th instruction, where the instruction index belongs to the supplied sequence (e.g., checking at instruction t1, t2, and so on).
- Checkpoint condition (C) — invokes checking when a Boolean condition C holds (e.g.,
(commit == 1)).
Role in the Tandem Simulation Flow
According to the refinement map and checkpoint map, the tandem generator automatically augments the instruction monitor block (one of the auxiliary blocks in the tandem simulation flow) to invoke the AV-Comparator at the appropriate moments. The instruction monitor uses the instruction map to detect instruction start/finish boundaries in the RTEM, while the checkpoint map determines the additional points at which AV comparison should be triggered.
See Also
- Refinement Map — the parent structure that contains the checkpoint map as one of its optional fields.
- Tandem Simulation — the simulation technique that consumes the checkpoint map to drive periodic AV comparisons.