Shared/Java: Add shared Guards library and switch Java to use it. #19573
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| private module LogicInput_v2 implements GuardsImpl::LogicInputSig { | ||
| private import semmle.code.java.dataflow.SSA as SSA |
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| /** | ||
| * Provides classes and predicates for determining "guard-controls" | ||
| * relationships. | ||
| * | ||
| * In their most general form, these relate a guard expression, a value, and a | ||
| * basic block, and state that execution of the basic block implies that | ||
| * control flow must have passed through the guard in order to reach the basic | ||
| * block, and when it did, the guard evaluated to the given value. | ||
| * | ||
| * For example, in `if (x == 0) { A }`, the guard `x == 0` evaluating to `true` | ||
| * controls the basic block `A`, in this case because the true branch dominates | ||
| * `A`, but more elaborate controls-relationships may also hold. | ||
| * For example, in | ||
| * ``` | ||
| * int sz = a != null ? a.length : 0; | ||
| * if (sz != 0) { | ||
| * // this block is controlled by: | ||
| * // sz != 0 evaluating to true | ||
| * // sz evaluating to not 0 | ||
| * // a.length evaluating to not 0 | ||
| * // a != null evaluating to true | ||
| * // a evaluating to not null | ||
| * } | ||
| * ``` | ||
| * | ||
| * The provided predicates are separated into general "controls" predicates and | ||
| * "directly controls" predicates. The former use all possible implication | ||
| * logic as described above, whereas the latter only use control flow dominance | ||
| * of the corresponding conditional successor edges. | ||
| * | ||
| * In some cases, a guard may have a successor edge that can be relevant for | ||
| * controlling the input to an SSA phi node, but does not dominate the | ||
| * preceeding block. To support this, the `hasBranchEdge` and | ||
| * `controlsBranchEdge` predicates are provided, where the former only uses the | ||
| * control flow graph similar to the `directlyControls` predicate, and the | ||
| * latter uses the full implication logic. | ||
| * | ||
| * All of these predicates are also available in the more general form that refers | ||
| * to `GuardValue`s instead of `boolean`s. | ||
| * | ||
| * The implementation is nested in two parameterized modules intended to | ||
| * facilitate multiple instantiations of the nested module with different | ||
| * precision levels. For example, more implications are available if the result | ||
| * of Range Analysis is available, but Range Analysis depends on Guards. This | ||
| * allows an initial instantiation of the `Logic` module without Range Analysis | ||
| * that can be used as input to Range Analysis, and a second instantiation | ||
| * using the result of Range Analysis to provide a final and more complete | ||
| * controls relation. | ||
| */ |
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