DeadCodeElimination
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package transforms
Add all shell (command line) options to an option parser
Add all shell (command line) options to an option parser
an option parser
Perform the transform, encode renaming with RenameMap, and can delete annotations Called by runTransform.
Perform the transform, encode renaming with RenameMap, and can delete annotations Called by runTransform.
Input Firrtl AST
A transformed Firrtl AST
Extract all References and SubFields from a possibly nested Expression
A convenience function useful for debugging and error messages
A convenience function useful for debugging and error messages
A sequence of transforms to add this transform as an optionalPrerequisite.
A sequence of transforms to add this transform as an optionalPrerequisite. The use of optionalPrerequisiteOf
enables the transform declaring them to always run before some other transforms. However, declaring
optionalPrerequisiteOf will not result in the sequence of transforms executing.
This is useful for providing an ordering constraint to guarantee that other transforms (e.g., emitters) will not be scheduled before you.
This method **will not** result in the listed transforms running. If you want to add multiple transforms at
once, you should use a DependencyManager with multiple targets.
All transforms that, if a prerequisite of *another* transform, will run before this transform.
All transforms that, if a prerequisite of *another* transform, will run before this transform.
The use of a Seq here is to preserve input order. Internally, this will be converted to a private, ordered Set.
A sequence of options provided
A sequence of options provided
All transform that must run before this transform
All transform that must run before this transform
The use of a Seq here is to preserve input order. Internally, this will be converted to a private, ordered Set.
Perform the transform and update annotations.
Perform the transform and update annotations.
Input Firrtl AST
A transformed Firrtl AST
A mathematical transform on some type
A mathematical transform on some type
an output object of the same type
All transforms that must run after this transform
All transforms that must run after this transform
This is a means of prerequisite injection into some other transform. Normally a transform will define its own prerequisites. Dependents exist for two main situations:
First, they improve the composition of optional transforms. If some first transform is optional (e.g., an expensive validation check), you would like to be able to conditionally cause it to run. If it is listed as a prerequisite on some other, second transform then it must always run before that second transform. There's no way to turn it off. However, by listing the second transform as a dependent of the first transform, the first transform will only run (and be treated as a prerequisite of the second transform) if included in a list of target transforms that should be run.
Second, an external library would like to inject some first transform before a second transform inside FIRRTL. In this situation, the second transform cannot have any knowledge of external libraries. The use of a dependent here allows for prerequisite injection into FIRRTL proper.
(Since version FIRRTL 1.3) Due to confusion, 'dependents' is being renamed to 'optionalPrerequisiteOf'. Override the latter instead.
The use of a Seq here is to preserve input order. Internally, this will be converted to a private, ordered Set.
firrtl.passes.CheckTypes for an example of an optional checking firrtl.Transform
Convenience method to get annotations relevant to this Transform
Convenience method to get annotations relevant to this Transform
The CircuitState form which to extract annotations
A collection of annotations
(Since version 1.1) Just collect the actual Annotation types the transform wants
(Since version FIRRTL 1.3) Use Dependency API methods for equivalent functionality. See: https://bit.ly/2Voppre
(Since version FIRRTL 1.3) Use Dependency API methods for equivalent functionality. See: https://bit.ly/2Voppre
Dead Code Elimination (DCE)
Performs DCE by constructing a global dependency graph starting with top-level outputs, external module ports, and simulation constructs as circuit sinks. External modules can optionally be eligible for DCE via the OptimizableExtModuleAnnotation.
Dead code is eliminated across module boundaries. Wires, ports, registers, and memories are all eligible for removal. Components marked with a DontTouchAnnotation will be treated as a circuit sink and thus anything that drives such a marked component will NOT be removed.
This transform preserves deduplication. All instances of a given firrtl.ir.DefModule are treated as the same individual module. Thus, while certain instances may have dead code due to the circumstances of their instantiation in their parent module, they will still not be removed. To remove such modules, use the NoDedupAnnotation to prevent deduplication.