Use Intrinsics#compare when specializing compareTo for ints

compiler/backend/src/org/jetbrains/kotlin/codegen/optimization/boxing/RedundantBoxingMethodTransformer.kt

@@ -453,19 +453,8 @@ class RedundantBoxingMethodTransformer : MethodTransformer() {
                 }
 
                 else -> {
-                    // Can't fuse with branching instruction.
+                    // Can't fuse with branching instruction. Use Intrinsics#compare(int, int).
-                    // Trick: convert I, I on stack to L, L and use LCMP.
+                    set(insn, MethodInsnNode(Opcodes.INVOKESTATIC, "kotlin/jvm/internal/Intrinsics", "compare", "(II)I", false))
-                    // This is more compact than explicit branching.
-                    // TODO Generate 'java.lang.Integer#compare(int, int)' in targets >= JVM 1.7
-
-                    // Initial stack: I1 I2
-                    insertBefore(insn, InsnNode(Opcodes.SWAP))       // I2 I1
-                    insertBefore(insn, InsnNode(Opcodes.I2L))        // L2 I1
-                    insertBefore(insn, InsnNode(Opcodes.DUP2_X1))    // L2 I1 L2
-                    insertBefore(insn, InsnNode(Opcodes.POP2))       // I1 L2
-                    insertBefore(insn, InsnNode(Opcodes.I2L))        // L1 L2
-                    insertBefore(insn, InsnNode(Opcodes.LCMP))       // compare(L1, L2)
-                    remove(insn)
                 }
             }
         }

compiler/testData/codegen/bytecodeText/boxingOptimization/intCompareTo.kt

@@ -0,0 +1,11 @@
+fun box(): String {
+    val a: Any = 1
+    val b: Any = 42
+    val test = (a as Comparable<Any>).compareTo(b)
+    if (test != -1) return "Fail: $test"
+
+    return "OK"
+}
+
+// 0 compareTo
+// 1 Intrinsics.compare

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

@@ -479,6 +479,12 @@ public class BytecodeTextTestGenerated extends AbstractBytecodeTextTest {
             doTest(fileName);
         }
 
+        @TestMetadata("intCompareTo.kt")
+        public void testIntCompareTo() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/bytecodeText/boxingOptimization/intCompareTo.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("kClassInAnnotation.kt")
         public void testKClassInAnnotation() throws Exception {
             String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/bytecodeText/boxingOptimization/kClassInAnnotation.kt");