Merge pull request #4319 from hvitved/python-java-block-precedes-var

Java/Python: Reduce size of `blockPrecedesVar`

csharp/ql/src/semmle/code/csharp/dataflow/SSA.qll

@@ -706,9 +706,9 @@ module Ssa {
 
     /**
      * Holds if `def` is accessed in basic block `bb1` (either a read or a write),
-     * `bb2` is a transitive successor of `bb1`, and `def` is *maybe* read in `bb2`
-     * or one of its transitive successors, but not in any block on the path between
-     * `bb1` and `bb2`.
+     * `bb2` is a transitive successor of `bb1`, `def` is live at the end of `bb1`,
+     * and the underlying variable for `def` is neither read nor written in any block
+     * on the path between `bb1` and `bb2`.
      */
     private predicate varBlockReaches(TrackedDefinition def, BasicBlock bb1, BasicBlock bb2) {
       varOccursInBlock(def, bb1, _) and

java/ql/src/semmle/code/java/dataflow/SSA.qll

@@ -770,7 +770,9 @@ private module SsaImpl {
 
     /** Holds if `v` occurs in `b` or one of `b`'s transitive successors. */
     private predicate blockPrecedesVar(TrackedVar v, BasicBlock b) {
-      varOccursInBlock(v, b.getABBSuccessor*())
+      varOccursInBlock(v, b)
+      or
+      ssaDefReachesEndOfBlock(v, _, b)
     }
 
     /**

java/ql/src/semmle/code/java/dataflow/internal/BaseSSA.qll

@@ -321,7 +321,9 @@ private module SsaImpl {
 
     /** Holds if `v` occurs in `b` or one of `b`'s transitive successors. */
     private predicate blockPrecedesVar(BaseSsaSourceVariable v, BasicBlock b) {
-      varOccursInBlock(v, b.getABBSuccessor*())
+      varOccursInBlock(v, b)
+      or
+      ssaDefReachesEndOfBlock(v, _, b)
     }
 
     /**

python/ql/src/semmle/python/essa/SsaCompute.qll

@@ -382,7 +382,9 @@ private module SsaComputeImpl {
 
     /** Holds if `v` occurs in `b` or one of `b`'s transitive successors. */
     private predicate blockPrecedesVar(SsaSourceVariable v, BasicBlock b) {
-      varOccursInBlock(v, b.getASuccessor*())
+      varOccursInBlock(v, b)
+      or
+      SsaDefinitionsImpl::reachesEndOfBlock(v, _, _, b)
     }
 
     /**