Python: cache exposed shared SSA adjacency relations

python/ql/lib/semmle/python/dataflow/new/internal/SsaImpl.qll

@@ -564,8 +564,10 @@ class EssaVariable extends Ssa::SsaDefinition {
  * library. Provides the same interface as legacy
  * `semmle.python.essa.SsaCompute::AdjacentUses`.
  */
+cached
 module AdjacentUses {
   /** Holds if `nodeFrom` and `nodeTo` are adjacent uses of the same SSA variable. */
+  cached
   predicate adjacentUseUse(Cfg::NameNode nodeFrom, Cfg::NameNode nodeTo) {
     exists(CfgImpl::BasicBlock bb1, int i1, CfgImpl::BasicBlock bb2, int i2 |
       Impl::adjacentUseUse(bb1, i1, bb2, i2, _, _) and
@@ -575,6 +577,7 @@ module AdjacentUses {
   }
 
   /** Holds if `use` is a first use of definition `def`. */
+  cached
   predicate firstUse(Ssa::SsaDefinition def, Cfg::NameNode use) {
     exists(CfgImpl::BasicBlock bb, int i |
       Impl::firstUse(def, bb, i, _) and
@@ -586,6 +589,7 @@ module AdjacentUses {
    * Holds if `use` is any reachable use of definition `def`. Combines
    * `firstUse` with transitive use-use adjacency.
    */
+  cached
   predicate useOfDef(Ssa::SsaDefinition def, Cfg::NameNode use) {
     firstUse(def, use)
     or

python/ql/test/library-tests/dataflow-new-ssa/AdjacentUsesContract.expected

@@ -0,0 +1,12 @@
+exposed_first_use_count
+| 9 |
+exposed_adjacent_use_count
+| 1 |
+exposed_use_of_def_count
+| 10 |
+first_use_projection_mismatch_count
+| 0 |
+adjacent_use_projection_mismatch_count
+| 0 |
+use_of_def_expansion_mismatch_count
+| 0 |

python/ql/test/library-tests/dataflow-new-ssa/AdjacentUsesContract.ql

@@ -0,0 +1,72 @@
+import python
+private import semmle.python.controlflow.internal.AstNodeImpl as CfgImpl
+private import semmle.python.controlflow.internal.Cfg as Cfg
+private import semmle.python.dataflow.new.internal.SsaImpl as SsaImpl
+
+private predicate projectedFirstUse(SsaImpl::Definition def, Cfg::NameNode use) {
+  exists(CfgImpl::BasicBlock bb, int i |
+    SsaImpl::Impl::firstUse(def, bb, i, _) and
+    use = bb.getNode(i)
+  )
+}
+
+private predicate projectedAdjacentUse(Cfg::NameNode nodeFrom, Cfg::NameNode nodeTo) {
+  exists(CfgImpl::BasicBlock bb1, int i1, CfgImpl::BasicBlock bb2, int i2 |
+    SsaImpl::Impl::adjacentUseUse(bb1, i1, bb2, i2, _, _) and
+    nodeFrom = bb1.getNode(i1) and
+    nodeTo = bb2.getNode(i2)
+  )
+}
+
+private predicate expandedUseOfDef(SsaImpl::Definition def, Cfg::NameNode use) {
+  exists(Cfg::NameNode first |
+    SsaImpl::AdjacentUses::firstUse(def, first) and
+    SsaImpl::AdjacentUses::adjacentUseUse*(first, use)
+  )
+}
+
+query int exposed_first_use_count() {
+  result =
+    count(SsaImpl::Definition def, Cfg::NameNode use | SsaImpl::AdjacentUses::firstUse(def, use))
+}
+
+query int exposed_adjacent_use_count() {
+  result =
+    count(Cfg::NameNode nodeFrom, Cfg::NameNode nodeTo |
+      SsaImpl::AdjacentUses::adjacentUseUse(nodeFrom, nodeTo)
+    )
+}
+
+query int exposed_use_of_def_count() {
+  result =
+    count(SsaImpl::Definition def, Cfg::NameNode use | SsaImpl::AdjacentUses::useOfDef(def, use))
+}
+
+query int first_use_projection_mismatch_count() {
+  result =
+    count(SsaImpl::Definition def, Cfg::NameNode use |
+      SsaImpl::AdjacentUses::firstUse(def, use) and not projectedFirstUse(def, use)
+      or
+      projectedFirstUse(def, use) and not SsaImpl::AdjacentUses::firstUse(def, use)
+    )
+}
+
+query int adjacent_use_projection_mismatch_count() {
+  result =
+    count(Cfg::NameNode nodeFrom, Cfg::NameNode nodeTo |
+      SsaImpl::AdjacentUses::adjacentUseUse(nodeFrom, nodeTo) and
+      not projectedAdjacentUse(nodeFrom, nodeTo)
+      or
+      projectedAdjacentUse(nodeFrom, nodeTo) and
+      not SsaImpl::AdjacentUses::adjacentUseUse(nodeFrom, nodeTo)
+    )
+}
+
+query int use_of_def_expansion_mismatch_count() {
+  result =
+    count(SsaImpl::Definition def, Cfg::NameNode use |
+      SsaImpl::AdjacentUses::useOfDef(def, use) and not expandedUseOfDef(def, use)
+      or
+      expandedUseOfDef(def, use) and not SsaImpl::AdjacentUses::useOfDef(def, use)
+    )
+}

python/ql/test/library-tests/dataflow-new-ssa/test.py

@@ -31,6 +31,11 @@ def basic_assign():  # $ def=basic_assign
     return y  # $ use=y
 
 
+def repeated_use(x):  # $ def=repeated_use def=x
+    first = x  # $ def=first use=x
+    return x + first  # $ use=x use=first
+
+
 def reassignment():  # $ def=reassignment
     x = 1
     x = 2  # $ def=x