Unified: Instantiate and expose public SSA api.

Author: aschackmull

unified/ql/lib/codeql/unified/internal/FacadeAst.qll

@@ -7,6 +7,7 @@ module;
 private import AstPlugin
 private import codeql.files.FileSystem
 private import codeql.unified.internal.NameBinding as NameBinding
+private import codeql.unified.internal.ControlFlowGraph::Public
 
 module Unified {
   private import Ast::Unified as G
@@ -124,6 +125,12 @@ module Unified {
       or
       result = this.getParent().(Argument).getParent()
     }
+
+    /** Gets the `ControlFlowNode` corresponding to this expression. */
+    ControlFlowNode getControlFlowNode() { result.injects(this) }
+
+    /** Gets the basic block containing this expression. */
+    BasicBlock getBasicBlock() { result = this.getControlFlowNode().getBasicBlock() }
   }
 
   class AccessorDeclaration extends G::AccessorDeclaration {

unified/ql/lib/codeql/unified/internal/dataflow/LocalSsa.qll

@@ -37,6 +37,53 @@ module LocalSsaOutput = Make<Location, Cfg, LocalSsaInput>;
 
 private import LocalSsaOutput
 
+private module SsaInput implements SsaInputSig {
+  private import codeql.unified.internal.ExprPositions
+
+  class Expr = U::Expr;
+
+  class Parameter = U::Parameter;
+
+  class VariableWrite instanceof BuilderNode {
+    private AstNode writeAccess;
+    private LocalVariable v;
+
+    VariableWrite() { this.isLocalVariableWrite(writeAccess, v) }
+
+    Expr asExpr() { hasIncomingValue(writeAccess, result) }
+
+    Expr getValue() {
+      exists(VariableDeclaration decl |
+        writeAccess = decl.getPattern() and result = decl.getValue()
+      )
+      or
+      exists(AssignExpr assignment |
+        writeAccess = assignment.getTarget() and result = assignment.getValue()
+      )
+      or
+      writeAccess = result.(CompoundAssignExpr).getTarget()
+      // TODO: Add case for prefix unary crement operations
+    }
+
+    predicate isParameterInit(Parameter p) { p.getPattern() = writeAccess }
+
+    string toString() { result = super.toString() }
+
+    Location getLocation() { result = super.getLocation() }
+  }
+
+  predicate explicitWrite(VariableWrite w, BasicBlock bb, int i, LocalSsaInput::SourceVariable v) {
+    exists(AstNode repr |
+      w.(BuilderNode).isLocalVariableWrite(repr, v) and
+      performsVariableAccess(repr, v, _, bb.getNode(i))
+    )
+  }
+}
+
+module SsaPublic {
+  module Ssa = MakeSsa<SsaInput>;
+}
+
 module LocalSsaDataFlowInput implements DataFlowIntegrationInputSig {
   class Expr = LocalVariableRefNode;
 

unified/ql/lib/unified.qll

@@ -9,4 +9,5 @@ import codeql.unified.internal.AstExtra::Public
 import codeql.unified.internal.ControlFlowGraph::Public
 import codeql.unified.internal.NameBinding::Public
 import codeql.unified.internal.dataflow.DataFlowPublic
+import codeql.unified.internal.dataflow.LocalSsa::SsaPublic
 import codeql.unified.internal.mad.LegacyMaD::Public