1.6 KiB
Basic control flow analysis
You can extract a basic control flow graph of the instructions in a method with the class BranchTargetFinder. The resulting graph is defined at the instruction level: each instruction is labeled with potential branch targets and branch origins.
BranchTargetFinder branchTargetFinder =
new BranchTargetFinder();
branchTargetFinder.visitCodeAttribute(clazz, method, codeAttribute);
Complete example: ApplyPeepholeOptimizations.java
Partial evaluation
You can extract more information from a method, with partial evaluation (often called abstract evaluation). You can tune the precision and the convergence speed by injecting different value factories and different invocation units:
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The value factories define the level of detail in representing values like integers or reference types. The values can be very generic (any primitive integer, a reference to any object) or more precise (the integer 42, or an integer between 0 and 5, or a non-null reference to an instance of java/lang/String).
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The invocation units define the values returned from retrieved fields and invoked methods. The values can again be very generic (any integer) or they can also be values that were cached in previous evaluations.
RangeValueFactory valueFactory = new RangeValueFactory( new ArrayReferenceValueFactory());
PartialEvaluator partialEvaluator = new PartialEvaluator( new BasicInvocationUnit(valueFactory), false);
partialEvaluator.visitCodeAttribute(clazz, method, codeAttribute);
Complete example: EvaluateCode.java