C#: Filter away phi (read) input steps from a node into itself

hvitved · hvitved · commit 165dc0b9bff6 · 2023-05-15T09:35:04.000+02:00
diff --git a/csharp/ql/lib/semmle/code/csharp/dataflow/internal/DataFlowPrivate.qll b/csharp/ql/lib/semmle/code/csharp/dataflow/internal/DataFlowPrivate.qll
@@ -335,7 +335,8 @@ module LocalFlow {
     exists(ControlFlow::BasicBlock bb, int i |
       SsaImpl::lastRefBeforeRedefExt(def, bb, i, next.getDefinitionExt()) and
       def.definesAt(_, bb, i, _) and
-      def = getSsaDefinitionExt(nodeFrom)
+      def = getSsaDefinitionExt(nodeFrom) and
+      nodeFrom != next
     )
   }
 
@@ -414,7 +415,8 @@ module LocalFlow {
     ) {
       exists(CIL::BasicBlock bb, int i | CilSsaImpl::lastRefBeforeRedefExt(def, bb, i, next) |
         def.definesAt(_, bb, i, _) and
-        def = nodeFrom.(CilSsaDefinitionExtNode).getDefinition()
+        def = nodeFrom.(CilSsaDefinitionExtNode).getDefinition() and
+        def != next
         or
         nodeFrom = TCilExprNode(bb.getNode(i).(CIL::ReadAccess))
       )

Original file line number	Diff line number	Diff line change
`@@ -335,7 +335,8 @@ module LocalFlow {`
`335`	`335`	`exists(ControlFlow::BasicBlock bb, int i \|`
`336`	`336`	`SsaImpl::lastRefBeforeRedefExt(def, bb, i, next.getDefinitionExt()) and`
`337`	`337`	`def.definesAt(_, bb, i, _) and`
`338`		`- def = getSsaDefinitionExt(nodeFrom)`
	`338`	`+ def = getSsaDefinitionExt(nodeFrom) and`
	`339`	`+ nodeFrom != next`
`339`	`340`	`)`
`340`	`341`	`}`
`341`	`342`
`@@ -414,7 +415,8 @@ module LocalFlow {`
`414`	`415`	`) {`
`415`	`416`	`exists(CIL::BasicBlock bb, int i \| CilSsaImpl::lastRefBeforeRedefExt(def, bb, i, next) \|`
`416`	`417`	`def.definesAt(_, bb, i, _) and`
`417`		`- def = nodeFrom.(CilSsaDefinitionExtNode).getDefinition()`
	`418`	`+ def = nodeFrom.(CilSsaDefinitionExtNode).getDefinition() and`
	`419`	`+ def != next`
`418`	`420`	`or`
`419`	`421`	`nodeFrom = TCilExprNode(bb.getNode(i).(CIL::ReadAccess))`
`420`	`422`	`)`