Don't add unused label if variables are absent

compiler/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/codegen/ExpressionCodegen.kt

@@ -289,7 +289,9 @@ class ExpressionCodegen(
         val info = BlockInfo(data)
         // Force materialization to avoid reading from out-of-scope variables.
         return super.visitBlock(expression, info).materialized.also {
-            writeLocalVariablesInTable(info, markNewLabel())
+            if (info.variables.isNotEmpty()) {
+                writeLocalVariablesInTable(info, markNewLabel())
+            }
         }
     }
 

compiler/testData/codegen/bytecodeText/disabledOptimizations/noUnusedLabel.kt

@@ -0,0 +1,16 @@
+// KOTLIN_CONFIGURATION_FLAGS: +JVM.DISABLE_OPTIMIZATION
+
+fun bar() {}
+
+fun foo(a: Boolean) { if (a) { foo(a) } }
+
+// method start
+// 5 L0
+
+//return
+// 3 L1
+
+// method end
+// 2 L2
+
+// 0 L3

compiler/tests/org/jetbrains/kotlin/codegen/BytecodeTextTestGenerated.java

@@ -1650,6 +1650,11 @@ public class BytecodeTextTestGenerated extends AbstractBytecodeTextTest {
         public void testNoUnitInstanceOnVoidFunctionCall() throws Exception {
             runTest("compiler/testData/codegen/bytecodeText/disabledOptimizations/noUnitInstanceOnVoidFunctionCall.kt");
         }
+
+        @TestMetadata("noUnusedLabel.kt")
+        public void testNoUnusedLabel() throws Exception {
+            runTest("compiler/testData/codegen/bytecodeText/disabledOptimizations/noUnusedLabel.kt");
+        }
     }
 
     @TestMetadata("compiler/testData/codegen/bytecodeText/enum")

compiler/tests/org/jetbrains/kotlin/codegen/ir/IrBytecodeTextTestGenerated.java

@@ -1605,6 +1605,11 @@ public class IrBytecodeTextTestGenerated extends AbstractIrBytecodeTextTest {
         public void testNoUnitInstanceOnVoidFunctionCall() throws Exception {
             runTest("compiler/testData/codegen/bytecodeText/disabledOptimizations/noUnitInstanceOnVoidFunctionCall.kt");
         }
+
+        @TestMetadata("noUnusedLabel.kt")
+        public void testNoUnusedLabel() throws Exception {
+            runTest("compiler/testData/codegen/bytecodeText/disabledOptimizations/noUnusedLabel.kt");
+        }
     }
 
     @TestMetadata("compiler/testData/codegen/bytecodeText/enum")