Backend upgrade with StringBuilder and string concatenation optimizations

compiler/test/dotty/tools/backend/jvm/StringConcatTest.scala

@@ -0,0 +1,129 @@
+package dotty.tools.backend.jvm
+
+import org.junit.runner.RunWith
+import org.junit.runners.JUnit4
+import org.junit.Test
+import scala.tools.asm.Opcodes._
+import org.junit.Assert._
+
+import ASMConverters._
+
+
+class StringConcatTest extends DottyBytecodeTest {
+  import ASMConverters._
+
+  @Test
+  def appendOverloadNoBoxing(): Unit = {
+    val code =
+      """class C {
+        |  def t1(
+        |         v: Unit,
+        |         z: Boolean,
+        |         c: Char,
+        |         b: Byte,
+        |         s: Short,
+        |         i: Int,
+        |         l: Long,
+        |         f: Float,
+        |         d: Double,
+        |         str: String,
+        |         sbuf: java.lang.StringBuffer,
+        |         chsq: java.lang.CharSequence,
+        |         chrs: Array[Char]) = str + this + v + z + c + b + s + i + f + l + d + sbuf + chsq + chrs
+        |
+        |  // similar, but starting off with any2stringadd
+        |  def t2(
+        |         v: Unit,
+        |         z: Boolean,
+        |         c: Char,
+        |         b: Byte,
+        |         s: Short,
+        |         i: Int,
+        |         l: Long,
+        |         f: Float,
+        |         d: Double,
+        |         str: String,
+        |         sbuf: java.lang.StringBuffer,
+        |         chsq: java.lang.CharSequence,
+        |         chrs: Array[Char]) = this + str + v + z + c + b + s + i + f + l + d + sbuf + chsq + chrs
+        |}
+      """.stripMargin
+
+    checkBCode(code) { dir =>
+      def instructions(meth: String): List[Instruction] = {
+        val clsIn = dir.lookupName("C.class", directory = false).input
+        val clsNode = loadClassNode(clsIn)
+        instructionsFromMethod(getMethod(clsNode, meth))
+      }
+
+      def invokeNameDesc(m: String): List[String] = instructions(m) collect {
+        case Invoke(_, _, name, desc, _) => name + desc
+      }
+
+      assertEquals(invokeNameDesc("t1"), List(
+        "<init>()V",
+        "append(Ljava/lang/String;)Ljava/lang/StringBuilder;",
+        "append(Ljava/lang/Object;)Ljava/lang/StringBuilder;",
+        "append(Ljava/lang/Object;)Ljava/lang/StringBuilder;",
+        "append(Z)Ljava/lang/StringBuilder;",
+        "append(C)Ljava/lang/StringBuilder;",
+        "append(I)Ljava/lang/StringBuilder;",
+        "append(I)Ljava/lang/StringBuilder;",
+        "append(I)Ljava/lang/StringBuilder;",
+        "append(F)Ljava/lang/StringBuilder;",
+        "append(J)Ljava/lang/StringBuilder;",
+        "append(D)Ljava/lang/StringBuilder;",
+        "append(Ljava/lang/StringBuffer;)Ljava/lang/StringBuilder;",
+        "append(Ljava/lang/CharSequence;)Ljava/lang/StringBuilder;",
+        "append(Ljava/lang/Object;)Ljava/lang/StringBuilder;", // test that we're not using the [C overload
+        "toString()Ljava/lang/String;"))
+
+      assertEquals(invokeNameDesc("t2"), List(
+        "any2stringadd(Ljava/lang/Object;)Ljava/lang/Object;",
+        "<init>()V",
+        "$plus$extension(Ljava/lang/Object;Ljava/lang/String;)Ljava/lang/String;",
+        "append(Ljava/lang/String;)Ljava/lang/StringBuilder;",
+        "append(Ljava/lang/Object;)Ljava/lang/StringBuilder;",
+        "append(Z)Ljava/lang/StringBuilder;",
+        "append(C)Ljava/lang/StringBuilder;",
+        "append(I)Ljava/lang/StringBuilder;",
+        "append(I)Ljava/lang/StringBuilder;",
+        "append(I)Ljava/lang/StringBuilder;",
+        "append(F)Ljava/lang/StringBuilder;",
+        "append(J)Ljava/lang/StringBuilder;",
+        "append(D)Ljava/lang/StringBuilder;",
+        "append(Ljava/lang/StringBuffer;)Ljava/lang/StringBuilder;",
+        "append(Ljava/lang/CharSequence;)Ljava/lang/StringBuilder;",
+        "append(Ljava/lang/Object;)Ljava/lang/StringBuilder;", // test that we're not using the [C overload
+        "toString()Ljava/lang/String;"))
+    }
+  }
+
+  @Test
+  def concatPrimitiveCorrectness(): Unit = {
+    val obj: Object = new { override def toString = "TTT" }
+    def t(
+           v: Unit,
+           z: Boolean,
+           c: Char,
+           b: Byte,
+           s: Short,
+           i: Int,
+           l: Long,
+           f: Float,
+           d: Double,
+           str: String,
+           sbuf: java.lang.StringBuffer,
+           chsq: java.lang.CharSequence,
+           chrs: Array[Char]) = {
+      val s1 = str + obj + v + z + c + b + s + i + f + l + d + sbuf + chsq + chrs
+      val s2 = obj + str + v + z + c + b + s + i + f + l + d + sbuf + chsq + chrs
+      s1 + "//" + s2
+    }
+    def sbuf = { val r = new java.lang.StringBuffer(); r.append("sbuf"); r }
+    def chsq: java.lang.CharSequence = "chsq"
+    val s = t((), true, 'd', 3: Byte, 12: Short, 3, -32l, 12.3f, -4.2d, "me", sbuf, chsq, Array('a', 'b'))
+    val r = s.replaceAll("""\[C@\w+""", "<ARRAY>")
+    assertEquals(r, "meTTT()trued312312.3-32-4.2sbufchsq<ARRAY>//TTTme()trued312312.3-32-4.2sbufchsq<ARRAY>")
+  }
+}