diff --git a/compiler/src/prog8/ast/expressions/AstExpressions.kt b/compiler/src/prog8/ast/expressions/AstExpressions.kt
index b59490dc5..9b61c9cc8 100644
--- a/compiler/src/prog8/ast/expressions/AstExpressions.kt
+++ b/compiler/src/prog8/ast/expressions/AstExpressions.kt
@@ -22,7 +22,7 @@ sealed class Expression: Node {
     abstract fun constValue(program: Program): NumericLiteralValue?
     abstract fun accept(visitor: IAstVisitor)
     abstract fun accept(visitor: AstWalker, parent: Node)
-    abstract fun referencesIdentifiers(vararg name: String): Boolean     // todo: remove this and add identifier usage tracking into CallGraph instead
+    abstract fun referencesIdentifiers(vararg name: String): Boolean
     abstract fun inferType(program: Program): InferredTypes.InferredType
 
     infix fun isSameAs(other: Expression): Boolean {
diff --git a/compiler/src/prog8/ast/processing/AstChecker.kt b/compiler/src/prog8/ast/processing/AstChecker.kt
index ff6983e85..3a86fd0fd 100644
--- a/compiler/src/prog8/ast/processing/AstChecker.kt
+++ b/compiler/src/prog8/ast/processing/AstChecker.kt
@@ -326,7 +326,7 @@ internal class AstChecker(private val program: Program,
     }
 
     override fun visit(repeatLoop: RepeatLoop) {
-        if(repeatLoop.untilCondition.referencesIdentifiers("A", "X", "Y"))   // TODO use callgraph?
+        if(repeatLoop.untilCondition.referencesIdentifiers("A", "X", "Y"))
             errors.warn("using a register in the loop condition is risky (it could get clobbered)", repeatLoop.untilCondition.position)
         if(repeatLoop.untilCondition.inferType(program).typeOrElse(DataType.STRUCT) !in IntegerDatatypes)
             errors.err("condition value should be an integer type", repeatLoop.untilCondition.position)
@@ -334,7 +334,7 @@ internal class AstChecker(private val program: Program,
     }
 
     override fun visit(whileLoop: WhileLoop) {
-        if(whileLoop.condition.referencesIdentifiers("A", "X", "Y"))        // TODO use callgraph?
+        if(whileLoop.condition.referencesIdentifiers("A", "X", "Y"))
             errors.warn("using a register in the loop condition is risky (it could get clobbered)", whileLoop.condition.position)
         if(whileLoop.condition.inferType(program).typeOrElse(DataType.STRUCT) !in IntegerDatatypes)
             errors.err("condition value should be an integer type", whileLoop.condition.position)
@@ -463,7 +463,6 @@ internal class AstChecker(private val program: Program,
         }
 
         // the initializer value can't refer to the variable itself (recursive definition)
-        // TODO use callgraph for check?
         if(decl.value?.referencesIdentifiers(decl.name) == true || decl.arraysize?.index?.referencesIdentifiers(decl.name) == true) {
             err("recursive var declaration")
         }
diff --git a/compiler/src/prog8/ast/statements/AstStatements.kt b/compiler/src/prog8/ast/statements/AstStatements.kt
index c838bea00..545a72346 100644
--- a/compiler/src/prog8/ast/statements/AstStatements.kt
+++ b/compiler/src/prog8/ast/statements/AstStatements.kt
@@ -668,8 +668,6 @@ class Subroutine(override val name: String,
             get() = statements.any { it.expensiveToInline }
 
     override lateinit var parent: Node
-    val calledBy = mutableListOf<Node>()            // TODO remove, use callgraph only
-    val calls = mutableSetOf<Subroutine>()          // TODO remove, use callgraph only
 
     val scopedname: String by lazy { makeScopedName(name) }
 
diff --git a/compiler/src/prog8/optimizer/CallGraph.kt b/compiler/src/prog8/optimizer/CallGraph.kt
index adaa56513..16253963f 100644
--- a/compiler/src/prog8/optimizer/CallGraph.kt
+++ b/compiler/src/prog8/optimizer/CallGraph.kt
@@ -57,15 +57,6 @@ class CallGraph(private val program: Program) : IAstVisitor {
 
             it.importedBy.addAll(importedBy.getValue(it))
             it.imports.addAll(imports.getValue(it))
-
-            forAllSubroutines(it) { sub ->
-                sub.calledBy.clear()
-                sub.calls.clear()
-
-                sub.calledBy.addAll(calledBy.getValue(sub))
-                sub.calls.addAll(calls.getValue(sub))
-            }
-
         }
 
         val rootmodule = program.modules.first()
diff --git a/compiler/src/prog8/optimizer/UnusedCodeRemover.kt b/compiler/src/prog8/optimizer/UnusedCodeRemover.kt
index d929bc2d2..9a78efded 100644
--- a/compiler/src/prog8/optimizer/UnusedCodeRemover.kt
+++ b/compiler/src/prog8/optimizer/UnusedCodeRemover.kt
@@ -17,7 +17,7 @@ internal class UnusedCodeRemover: AstWalker() {
         val entrypoint = program.entrypoint()
         program.modules.forEach {
             callgraph.forAllSubroutines(it) { sub ->
-                if (sub !== entrypoint && !sub.keepAlways && (sub.calledBy.isEmpty() || (sub.containsNoCodeNorVars() && !sub.isAsmSubroutine)))
+                if (sub !== entrypoint && !sub.keepAlways && (callgraph.calledBy[sub].isNullOrEmpty() || (sub.containsNoCodeNorVars() && !sub.isAsmSubroutine)))
                     removals.add(IAstModification.Remove(sub, sub.definingScope() as Node))
             }
         }