diff --git a/compiler/frontend/src/org/jetbrains/jet/lang/cfg/pseudocode/instructions/Instruction.kt b/compiler/frontend/src/org/jetbrains/jet/lang/cfg/pseudocode/instructions/Instruction.kt
index e98ff49cdb0..ea2df5fbe4e 100644
--- a/compiler/frontend/src/org/jetbrains/jet/lang/cfg/pseudocode/instructions/Instruction.kt
+++ b/compiler/frontend/src/org/jetbrains/jet/lang/cfg/pseudocode/instructions/Instruction.kt
@@ -23,7 +23,7 @@ import org.jetbrains.jet.lang.cfg.pseudocode.PseudoValue
 public trait Instruction {
     public var owner: Pseudocode
 
-    public val previousInstructions: MutableCollection<Instruction>
+    public val previousInstructions: Collection<Instruction>
     public val nextInstructions: Collection<Instruction>
 
     public val dead: Boolean
@@ -32,7 +32,7 @@ public trait Instruction {
 
     public val inputValues: List<PseudoValue>
 
-    public fun getCopies(): Collection<Instruction>
+    public val copies: Collection<Instruction>
 
     public fun accept(visitor: InstructionVisitor)
     public fun <R> accept(visitor: InstructionVisitorWithResult<R>): R
diff --git a/compiler/frontend/src/org/jetbrains/jet/lang/cfg/pseudocode/instructions/InstructionImpl.kt b/compiler/frontend/src/org/jetbrains/jet/lang/cfg/pseudocode/instructions/InstructionImpl.kt
index 45b4cb11df0..3318a932b83 100644
--- a/compiler/frontend/src/org/jetbrains/jet/lang/cfg/pseudocode/instructions/InstructionImpl.kt
+++ b/compiler/frontend/src/org/jetbrains/jet/lang/cfg/pseudocode/instructions/InstructionImpl.kt
@@ -33,46 +33,32 @@ public abstract class InstructionImpl(public override val lexicalScope: LexicalS
             _owner = value
         }
 
-    private val _copies = HashSet<Instruction>()
+    private var allCopies: MutableSet<InstructionImpl>? = null
 
-    override fun getCopies(): Collection<Instruction> {
-        return original?.let { original ->
-            val originalCopies = Sets.newHashSet(original.getCopies())
-            originalCopies.remove(this)
-            originalCopies.add(original)
-            originalCopies
-        } ?: _copies
-    }
+    override val copies: Collection<Instruction>
+        get() = allCopies?.filter { it != this } ?: Collections.emptyList()
 
-    private var original: Instruction? = null
-
-    private fun setOriginalInstruction(value: Instruction?) {
-        assert(original == null) { "Instruction can't have two originals: this.original = ${original}; new original = $this" }
-        original = value
-    }
-
-    public fun copy(): Instruction {
-        return updateCopyInfo(createCopy())
-    }
+    fun copy(): Instruction = updateCopyInfo(createCopy())
 
     protected abstract fun createCopy(): InstructionImpl
 
     protected fun updateCopyInfo(instruction: InstructionImpl): Instruction {
-        _copies.add(instruction)
-        instruction.setOriginalInstruction(this)
+        if (allCopies == null) {
+            allCopies = hashSetOf(this)
+        }
+        instruction.allCopies = allCopies
+        allCopies!!.add(instruction)
         return instruction
     }
 
     public var markedAsDead: Boolean = false
 
-    override val dead: Boolean get() = markedAsDead && getCopies().all { (it as InstructionImpl).markedAsDead }
+    override val dead: Boolean get() = allCopies?.all { it.markedAsDead } ?: markedAsDead
 
     override val previousInstructions: MutableCollection<Instruction> = LinkedHashSet()
 
     protected fun outgoingEdgeTo(target: Instruction?): Instruction? {
-        if (target != null) {
-            target.previousInstructions.add(this)
-        }
+        (target as InstructionImpl?)?.previousInstructions?.add(this)
         return target
     }