The constant optimization phase.
A standard phase template
The global environment; overridden by instantiation in Global.
The global environment; overridden by instantiation in Global.
List of phase names, this phase should run after
List of phase names, this phase should run after
Phase name this phase will attach itself to, not allowing any phase to come between it and the phase name declared
Phase name this phase will attach itself to, not allowing any phase to come between it and the phase name declared
SubComponent are added to a HashSet and two phases are the same if they have the same name
SubComponent are added to a HashSet and two phases are the same if they have the same name
Internal flag to tell external from internal phases
Internal flag to tell external from internal phases
Create a new phase
Create a new phase
The phase corresponding to this subcomponent in the current compiler run
The phase corresponding to this subcomponent in the current compiler run
The name of the phase
The name of the phase
New flags defined by the phase which are not valid before
New flags defined by the phase which are not valid before
New flags defined by the phase which are not valid until immediately after it
New flags defined by the phase which are not valid until immediately after it
List of phase names, this phase should run before
List of phase names, this phase should run before
ConstantOptimization uses abstract interpretation to approximate for each instruction what constants a variable or stack slot might hold or cannot hold. From this it will eliminate unreachable conditionals where only one branch is reachable, e.g. to eliminate unnecessary null checks.
With some more work it could be extended to - cache stable values (final fields, modules) in locals - replace the copy propagation in ClosureElilmination - fold constants - eliminate unnecessary stores and loads - propagate knowledge gathered from conditionals for further optimization