Shared/Java: Introduce a shared control flow reachability library and replace the Java Nullness implementation.

java/ql/lib/semmle/code/java/controlflow/ControlFlow.qll

@@ -0,0 +1,60 @@
+/**
+ * Provides an implementation of local (intraprocedural) control flow reachability.
+ */
+overlay[local?]
+module;
+
+import java
+private import codeql.controlflow.ControlFlow
+private import semmle.code.java.dataflow.SSA as SSA
+private import semmle.code.java.controlflow.Guards as Guards
+
+private module ControlFlowInput implements InputSig<Location, ControlFlowNode, BasicBlock> {
+  private import java as J
+
+  AstNode getEnclosingAstNode(ControlFlowNode node) { node.getAstNode() = result }
+
+  class AstNode = ExprParent;
+
+  AstNode getParent(AstNode node) {
+    result = node.(Expr).getParent() or
+    result = node.(Stmt).getParent()
+  }
+
+  class FinallyBlock extends AstNode {
+    FinallyBlock() { any(TryStmt try).getFinally() = this }
+  }
+
+  class Expr = J::Expr;
+
+  class SourceVariable = SSA::SsaSourceVariable;
+
+  class SsaDefinition = SSA::SsaVariable;
+
+  class SsaWriteDefinition extends SsaDefinition instanceof SSA::SsaExplicitUpdate {
+    Expr getDefinition() {
+      super.getDefiningExpr().(VariableAssign).getSource() = result or
+      super.getDefiningExpr().(AssignOp) = result
+    }
+  }
+
+  class SsaPhiNode = SSA::SsaPhiNode;
+
+  class SsaUncertainDefinition extends SsaDefinition instanceof SSA::SsaUncertainImplicitUpdate {
+    SsaDefinition getPriorDefinition() { result = super.getPriorDef() }
+  }
+
+  class GuardValue = Guards::GuardValue;
+
+  predicate ssaControlsBranchEdge(SsaDefinition def, BasicBlock bb1, BasicBlock bb2, GuardValue v) {
+    Guards::Guards_v3::ssaControlsBranchEdge(def, bb1, bb2, v)
+  }
+
+  predicate ssaControls(SsaDefinition def, BasicBlock bb, GuardValue v) {
+    Guards::Guards_v3::ssaControls(def, bb, v)
+  }
+
+  import Guards::Guards_v3::InternalUtil
+}
+
+module ControlFlow = Make<Location, Cfg, ControlFlowInput>;