KT-17110 Rewrite branches targeting other branches

- Rewrite branches targeting other branches to target directly the
final destination to avoid runtime performance penalties.

Fix of https://youtrack.jetbrains.com/issue/KT-17110

compiler/backend/src/org/jetbrains/kotlin/codegen/optimization/RedundantGotoMethodTransformer.kt

@@ -22,31 +22,76 @@ import org.jetbrains.org.objectweb.asm.Opcodes
 import org.jetbrains.org.objectweb.asm.tree.AbstractInsnNode
 import org.jetbrains.org.objectweb.asm.tree.JumpInsnNode
 import org.jetbrains.org.objectweb.asm.tree.LabelNode
+import org.jetbrains.org.objectweb.asm.tree.LineNumberNode
 import org.jetbrains.org.objectweb.asm.tree.MethodNode
 
 class RedundantGotoMethodTransformer : MethodTransformer() {
     /**
-     * Removes redundant GOTO's, i.e. to subsequent labels
+     * Removes redundant GOTO's in the following cases:
+     *  (1) subsequent labels
+     *      ...
+     *      goto Label (can be removed)
+     *      Label:
+     *      ...
+     *  (2) indirect goto
+     *      ...
+     *      <branch instruction> Label (can be rewrote to <branch instruction> Label2)
+     *      ...
+     *      Label:
+     *      goto Label2 (must not be removed due to the previous instruction that can fallthrough on this goto)
+     *      ...
      */
     override fun transform(internalClassName: String, methodNode: MethodNode) {
         val insns = methodNode.instructions.toArray().apply { reverse() }
-        val insnsToRemove = arrayListOf<AbstractInsnNode>()
-
+        var insnsToRemove = arrayListOf<AbstractInsnNode>()
         val currentLabels = hashSetOf<LabelNode>()
+        var labelsToReplace = hashMapOf<LabelNode, JumpInsnNode>()
+        var pendingGoto: JumpInsnNode? = null
+
         for (insn in insns) {
             when {
-                insn is LabelNode ->
+                insn is LabelNode -> {
                     currentLabels.add(insn)
-                insn.opcode == Opcodes.GOTO &&
-                        (insn as JumpInsnNode).label in currentLabels ->
-                    insnsToRemove.add(insn)
-                insn.isMeaningful ->
+                    pendingGoto?.let { labelsToReplace[insn] = it }
+                }
+                insn.opcode == Opcodes.GOTO -> {
+                    pendingGoto = insn as JumpInsnNode
+                    if (insn.label in currentLabels) {
+                        insnsToRemove.add(insn)
+                    } else {
+                        currentLabels.clear()
+                    }
+                }
+                insn is LineNumberNode -> pendingGoto = null
+                insn.isMeaningful -> {
                     currentLabels.clear()
+                    pendingGoto = null
+                }
             }
         }
 
+        // Rewrite branch instructions.
+        if (!labelsToReplace.isEmpty()) {
+            insns.filter { it is JumpInsnNode }.forEach { rewriteLabelIfNeeded(it as JumpInsnNode, labelsToReplace) }
+        }
+
         for (insnToRemove in insnsToRemove) {
             methodNode.instructions.remove(insnToRemove)
         }
     }
+
+    private fun rewriteLabelIfNeeded(
+        jumpInsn: JumpInsnNode,
+        labelsToReplace: HashMap<LabelNode, JumpInsnNode>
+    ) {
+        getLastTargetJumpInsn(jumpInsn, labelsToReplace).takeIf { it.label != jumpInsn.label }?.let {
+            // Do not remove the old label because it can be used to define a local variable range.
+            jumpInsn.label = it.label
+        }
+    }
+
+    private fun getLastTargetJumpInsn(jumpInsn: JumpInsnNode, labelsToReplace: HashMap<LabelNode, JumpInsnNode>): JumpInsnNode {
+        labelsToReplace[jumpInsn.label]?.let { return getLastTargetJumpInsn(it, labelsToReplace) }
+        return jumpInsn
+    }
 }

compiler/testData/codegen/box/controlStructures/kt17110.kt

@@ -0,0 +1,20 @@
+
+fun test(x: Int, y: Int): String {
+    var result: String
+    if (x == 6) {
+        if (y == 6) {
+            result = "a"
+        } else {
+            result = "b"
+        }
+    } else {
+        result = "c"
+    }
+    return result
+}
+
+fun box(): String {
+    if (test(9, 10) != "c")
+        return "Failures"
+    return "OK"
+}

compiler/testData/codegen/bytecodeText/controlStructures/kt17110.kt

@@ -0,0 +1,21 @@
+fun test(x: Int, y: Int): String {
+    var result: String
+    if (x == 6) {
+        if (y == 6) {
+            result = "a"
+        } else {
+            result = "b"
+        }
+    } else {
+        result = "c"
+    }
+    return result
+}
+
+fun box(): String {
+    if (test(9, 10) != "c")
+        return "Failures"
+    return "OK"
+}
+
+// 2 GOTO L7

compiler/tests-ir-jvm/tests/org/jetbrains/kotlin/codegen/ir/IrBlackBoxCodegenTestGenerated.java

@@ -4800,6 +4800,12 @@ public class IrBlackBoxCodegenTestGenerated extends AbstractIrBlackBoxCodegenTes
             doTest(fileName);
         }
 
+        @TestMetadata("kt17110.kt")
+        public void testKt17110() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/controlStructures/kt17110.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("kt1742.kt")
         public void testKt1742() throws Exception {
             String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/controlStructures/kt1742.kt");

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

@@ -4800,6 +4800,12 @@ public class BlackBoxCodegenTestGenerated extends AbstractBlackBoxCodegenTest {
             doTest(fileName);
         }
 
+        @TestMetadata("kt17110.kt")
+        public void testKt17110() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/controlStructures/kt17110.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("kt1742.kt")
         public void testKt1742() throws Exception {
             String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/controlStructures/kt1742.kt");

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

@@ -1069,6 +1069,21 @@ public class BytecodeTextTestGenerated extends AbstractBytecodeTextTest {
         }
     }
 
+    @TestMetadata("compiler/testData/codegen/bytecodeText/controlStructures")
+    @TestDataPath("$PROJECT_ROOT")
+    @RunWith(JUnit3RunnerWithInners.class)
+    public static class ControlStructures extends AbstractBytecodeTextTest {
+        public void testAllFilesPresentInControlStructures() throws Exception {
+            KotlinTestUtils.assertAllTestsPresentByMetadata(this.getClass(), new File("compiler/testData/codegen/bytecodeText/controlStructures"), Pattern.compile("^(.+)\\.kt$"), TargetBackend.ANY, true);
+        }
+
+        @TestMetadata("kt17110.kt")
+        public void testKt17110() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/bytecodeText/controlStructures/kt17110.kt");
+            doTest(fileName);
+        }
+    }
+
     @TestMetadata("compiler/testData/codegen/bytecodeText/coroutines")
     @TestDataPath("$PROJECT_ROOT")
     @RunWith(JUnit3RunnerWithInners.class)

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

@@ -4800,6 +4800,12 @@ public class LightAnalysisModeTestGenerated extends AbstractLightAnalysisModeTes
             doTest(fileName);
         }
 
+        @TestMetadata("kt17110.kt")
+        public void testKt17110() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/controlStructures/kt17110.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("kt1742.kt")
         public void testKt1742() throws Exception {
             String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/controlStructures/kt1742.kt");

js/js.tests/test/org/jetbrains/kotlin/js/test/semantics/JsCodegenBoxTestGenerated.java

@@ -5334,6 +5334,12 @@ public class JsCodegenBoxTestGenerated extends AbstractJsCodegenBoxTest {
             doTest(fileName);
         }
 
+        @TestMetadata("kt17110.kt")
+        public void testKt17110() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/controlStructures/kt17110.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("kt1742.kt")
         public void testKt1742() throws Exception {
             String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/controlStructures/kt1742.kt");