SSA: Restrict size of TNode

Author: hvitved

shared/ssa/codeql/ssa/Ssa.qll

@@ -1224,7 +1224,14 @@ module Make<LocationSig Location, InputSig<Location> Input> {
   module DataFlowIntegration<DataFlowIntegrationInputSig DfInput> {
     private import codeql.util.Boolean
 
-    final private class DefinitionExtFinal = DefinitionExt;
+    pragma[nomagic]
+    private DfInput::Expr getARead(Definition def) {
+      exists(SourceVariable v, BasicBlock bb, int i |
+        ssaDefReachesRead(v, def, bb, i) and
+        variableRead(bb, i, v, true) and
+        result.hasCfgNode(bb, i)
+      )
+    }
 
     pragma[nomagic]
     private predicate adjacentDefReachesReadExt(
@@ -1291,6 +1298,8 @@ module Make<LocationSig Location, InputSig<Location> Input> {
       )
     }
 
+    final private class DefinitionExtFinal = DefinitionExt;
+
     /** An SSA definition into which another SSA definition may flow. */
     private class SsaInputDefinitionExt extends DefinitionExtFinal {
       SsaInputDefinitionExt() {
@@ -1311,13 +1320,11 @@ module Make<LocationSig Location, InputSig<Location> Input> {
 
     cached
     private newtype TNode =
-      TParamNode(DfInput::Parameter p) or
+      TParamNode(DfInput::Parameter p) { DfInput::ssaDefInitializesParam(_, p) } or
       TExprNode(DfInput::Expr e, Boolean isPost) {
-        exists(BasicBlock bb, int i |
-          variableRead(bb, i, _, true) and
-          e.hasCfgNode(bb, i)
-        )
+        e = getARead(_)
         or
+        DfInput::ssaDefAssigns(_, e) and
         isPost = false
       } or
       TSsaDefinitionNode(DefinitionExt def) or
@@ -1574,15 +1581,6 @@ module Make<LocationSig Location, InputSig<Location> Input> {
       isUseStep = false
     }
 
-    pragma[nomagic]
-    private DfInput::Expr getARead(Definition def) {
-      exists(SourceVariable v, BasicBlock bb, int i |
-        ssaDefReachesRead(v, def, bb, i) and
-        variableRead(bb, i, v, true) and
-        result.hasCfgNode(bb, i)
-      )
-    }
-
     /** Holds if the value of `nodeTo` is given by `nodeFrom`. */
     predicate localMustFlowStep(DefinitionExt def, Node nodeFrom, Node nodeTo) {
       (