Java: Rework adjacentUseUse

Author: hvitved

java/ql/lib/semmle/code/java/dataflow/internal/SsaImpl.qll

@@ -89,11 +89,6 @@ private ControlFlowNode captureNode(TrackedVar capturedvar, TrackedVar closureva
   )
 }
 
-/** Holds if `VarAccess` `use` of `v` occurs in `b` at index `i`. */
-private predicate variableUse(TrackedVar v, VarRead use, BasicBlock b, int i) {
-  v.getAnAccess() = use and b.getNode(i) = use
-}
-
 /** Holds if the value of `v` is captured in `b` at index `i`. */
 private predicate variableCapture(TrackedVar capturedvar, TrackedVar closurevar, BasicBlock b, int i) {
   b.getNode(i) = captureNode(capturedvar, closurevar)
@@ -177,66 +172,6 @@ class UntrackedDef extends Definition {
   Location getLocation() { result = read.getLocation() }
 }
 
-pragma[noinline]
-private predicate adjacentDefRead(
-  Definition def, SsaInput::BasicBlock bb1, int i1, SsaInput::BasicBlock bb2, int i2,
-  SsaInput::SourceVariable v
-) {
-  Impl::adjacentDefRead(def, bb1, i1, bb2, i2) and
-  v = def.getSourceVariable()
-}
-
-pragma[nomagic]
-predicate adjacentDefReachesRead(
-  Definition def, SsaInput::SourceVariable v, SsaInput::BasicBlock bb1, int i1,
-  SsaInput::BasicBlock bb2, int i2
-) {
-  adjacentDefRead(def, bb1, i1, bb2, i2, v) and
-  (
-    def.definesAt(v, bb1, i1)
-    or
-    SsaInput::variableRead(bb1, i1, v, true)
-  )
-  or
-  exists(SsaInput::BasicBlock bb3, int i3 |
-    adjacentDefReachesRead(def, v, bb1, i1, bb3, i3) and
-    SsaInput::variableRead(bb3, i3, _, false) and
-    Impl::adjacentDefRead(def, bb3, i3, bb2, i2)
-  )
-}
-
-/** Same as `adjacentDefRead`, but skips uncertain reads. */
-pragma[nomagic]
-private predicate adjacentDefSkipUncertainReads(
-  Definition def, SsaInput::BasicBlock bb1, int i1, SsaInput::BasicBlock bb2, int i2
-) {
-  exists(SsaInput::SourceVariable v |
-    adjacentDefReachesRead(def, v, bb1, i1, bb2, i2) and
-    SsaInput::variableRead(bb2, i2, v, true)
-  )
-}
-
-pragma[nomagic]
-private predicate adjacentDefReachesUncertainRead(
-  Definition def, SsaInput::BasicBlock bb1, int i1, SsaInput::BasicBlock bb2, int i2
-) {
-  exists(SsaInput::SourceVariable v |
-    adjacentDefReachesRead(def, v, bb1, i1, bb2, i2) and
-    SsaInput::variableRead(bb2, i2, v, false)
-  )
-}
-
-pragma[nomagic]
-predicate lastRefBeforeRedef(Definition def, BasicBlock bb, int i, Definition next) {
-  Impl::lastRefRedef(def, bb, i, next) and
-  not SsaInput::variableRead(bb, i, def.getSourceVariable(), false)
-  or
-  exists(SsaInput::BasicBlock bb0, int i0 |
-    Impl::lastRefRedef(def, bb0, i0, next) and
-    adjacentDefReachesUncertainRead(def, bb, i, bb0, i0)
-  )
-}
-
 cached
 private module Cached {
   cached
@@ -556,12 +491,27 @@ private module Cached {
     )
   }
 
+  pragma[nomagic]
+  private predicate captureDefReaches(Definition def, SsaInput::BasicBlock bb2, int i2) {
+    variableCapture(def.getSourceVariable(), _, _, _) and
+    exists(SsaInput::BasicBlock bb1, int i1 |
+      Impl::adjacentDefRead(def, bb1, i1, bb2, i2) and
+      def.definesAt(_, bb1, i1)
+    )
+    or
+    exists(SsaInput::BasicBlock bb3, int i3 |
+      captureDefReaches(def, bb3, i3) and
+      SsaInput::variableRead(bb3, i3, _, _) and
+      Impl::adjacentDefRead(def, bb3, i3, bb2, i2)
+    )
+  }
+
   /** Holds if `init` is a closure variable that captures the value of `capturedvar`. */
   cached
   predicate captures(SsaImplicitInit init, SsaVariable capturedvar) {
-    exists(BasicBlock bb2, int i2 |
-      adjacentDefReachesRead(capturedvar, _, _, _, bb2, i2) and
-      variableCapture(capturedvar.getSourceVariable(), init.getSourceVariable(), bb2, i2)
+    exists(BasicBlock bb, int i |
+      captureDefReaches(capturedvar, bb, i) and
+      variableCapture(capturedvar.getSourceVariable(), init.getSourceVariable(), bb, i)
     )
   }
 
@@ -574,16 +524,22 @@ private module Cached {
     Impl::uncertainWriteDefinitionInput(redef, def)
   }
 
-  /**
-   * Holds if the value defined at SSA definition `def` can reach a read at `use`,
-   * without passing through any other read.
-   */
   pragma[nomagic]
-  private predicate firstUseSameVar(Definition def, VarRead use) {
-    exists(BasicBlock bb1, int i1, BasicBlock bb2, int i2 |
-      def.definesAt(_, bb1, i1) and
-      adjacentDefSkipUncertainReads(def, bb1, i1, bb2, i2) and
-      use = bb2.getNode(i2)
+  private predicate defReaches(Definition def, DataFlowIntegration::Node node) {
+    exists(DataFlowIntegration::SsaDefinitionExtNode nodeFrom |
+      nodeFrom.getDefinitionExt() = def and
+      DataFlowIntegrationImpl::localFlowStep(_, nodeFrom, node, false)
+    )
+    or
+    exists(DataFlowIntegration::Node mid |
+      defReaches(def, mid) and
+      DataFlowIntegrationImpl::localFlowStep(_, mid, node, _)
+    |
+      // flow into phi input node
+      mid instanceof DataFlowIntegration::SsaInputNode
+      or
+      // flow into definition
+      mid instanceof DataFlowIntegration::SsaDefinitionExtNode
     )
   }
 
@@ -593,14 +549,9 @@ private module Cached {
    */
   cached
   predicate firstUse(Definition def, VarRead use) {
-    firstUseSameVar(def, use)
-    or
-    exists(Definition redef, BasicBlock b1, int i1 |
-      redef instanceof SsaUncertainImplicitUpdate or redef instanceof SsaPhiNode
-    |
-      lastRefBeforeRedef(def, b1, i1, redef) and
-      def.definesAt(_, b1, i1) and
-      firstUse(redef, use)
+    exists(DataFlowIntegration::ExprNode nodeTo |
+      nodeTo.getExpr() = use and
+      defReaches(def, nodeTo)
     )
   }
 
@@ -646,17 +597,41 @@ private module Cached {
 
   cached
   module SsaPublic {
+    pragma[nomagic]
+    private predicate useReaches(VarRead use, DataFlowIntegration::Node node, boolean sameVar) {
+      exists(DataFlowIntegration::ExprNode nodeFrom |
+        nodeFrom.getExpr() = use and
+        DataFlowIntegration::localFlowStep(_, nodeFrom, node, true) and
+        sameVar = true
+      )
+      or
+      exists(DataFlowIntegration::Node mid, boolean sameVarMid |
+        useReaches(use, mid, sameVarMid) and
+        DataFlowIntegration::localFlowStep(_, mid, node, _)
+      |
+        // flow into phi input node
+        mid instanceof DataFlowIntegration::SsaInputNode and
+        sameVar = false
+        or
+        // flow into definition
+        exists(Impl::DefinitionExt def |
+          def = mid.(DataFlowIntegration::SsaDefinitionExtNode).getDefinitionExt()
+        |
+          if def instanceof Impl::PhiReadNode then sameVar = sameVarMid else sameVar = false
+        )
+      )
+    }
+
     /**
      * Holds if `use1` and `use2` form an adjacent use-use-pair of the same SSA
      * variable, that is, the value read in `use1` can reach `use2` without passing
      * through any other use or any SSA definition of the variable.
      */
     cached
     predicate adjacentUseUseSameVar(VarRead use1, VarRead use2) {
-      exists(TrackedVar v, BasicBlock b1, int i1, BasicBlock b2, int i2 |
-        adjacentDefSkipUncertainReads(_, b1, i1, b2, i2) and
-        variableUse(v, use1, b1, i1) and
-        variableUse(v, use2, b2, i2)
+      exists(DataFlowIntegration::ExprNode nodeTo |
+        nodeTo.getExpr() = use2 and
+        useReaches(use1, nodeTo, true)
       )
     }
 
@@ -668,14 +643,9 @@ private module Cached {
      */
     cached
     predicate adjacentUseUse(VarRead use1, VarRead use2) {
-      adjacentUseUseSameVar(use1, use2)
-      or
-      exists(TrackedSsaDef def, BasicBlock b1, int i1 |
-        lastRefBeforeRedef(_, b1, i1, def) and
-        variableUse(_, use1, b1, i1) and
-        firstUse(def, use2)
-      |
-        def instanceof SsaUncertainImplicitUpdate or def instanceof SsaPhiNode
+      exists(DataFlowIntegration::ExprNode nodeTo |
+        nodeTo.getExpr() = use2 and
+        useReaches(use1, nodeTo, _)
       )
     }
   }