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package scala.tools.nsc
package backend.jvm
package opt
import org.junit.runner.RunWith
import org.junit.runners.JUnit4
import org.junit.Test
import scala.tools.asm.Opcodes._
import org.junit.Assert._
import scala.collection.JavaConverters._
import CodeGenTools._
import scala.tools.partest.ASMConverters
import ASMConverters._
import scala.tools.testing.ClearAfterClass
object UnusedLocalVariablesTest extends ClearAfterClass.Clearable {
var dceCompiler = newCompiler(extraArgs = "-Ybackend:GenBCode -Yopt:unreachable-code")
def clear(): Unit = { dceCompiler = null }
}
@RunWith(classOf[JUnit4])
class UnusedLocalVariablesTest extends ClearAfterClass {
ClearAfterClass.stateToClear = UnusedLocalVariablesTest
val dceCompiler = UnusedLocalVariablesTest.dceCompiler
@Test
def removeUnusedVar(): Unit = {
val code = """def f(a: Long, b: String, c: Double): Unit = { return; var x = a; var y = x + 10 }"""
assertLocalVarCount(code, 4) // `this, a, b, c`
val code2 = """def f(): Unit = { var x = if (true) return else () }"""
assertLocalVarCount(code2, 1) // x is eliminated, constant folding in scalac removes the if
val code3 = """def f: Unit = return""" // paramless method
assertLocalVarCount(code3, 1) // this
}
@Test
def keepUsedVar(): Unit = {
val code = """def f(a: Long, b: String, c: Double): Unit = { val x = 10 + a; val y = x + 10 }"""
assertLocalVarCount(code, 6)
val code2 = """def f(a: Long): Unit = { var x = if (a == 0l) return else () }"""
assertLocalVarCount(code2, 3) // remains
}
@Test
def constructorLocals(): Unit = {
val code = """class C {
| def this(a: Int) = {
| this()
| throw new Exception("")
| val y = 0
| }
|}
|""".stripMargin
val cls = compileClasses(dceCompiler)(code).head
val m = convertMethod(cls.methods.asScala.toList.find(_.desc == "(I)V").get)
assertTrue(m.localVars.length == 2) // this, a, but not y
val code2 =
"""class C {
| {
| throw new Exception("")
| val a = 0
| }
|}
|
|object C {
| {
| throw new Exception("")
| val b = 1
| }
|}
""".stripMargin
val clss2 = compileClasses(dceCompiler)(code2)
val cls2 = clss2.find(_.name == "C").get
val companion2 = clss2.find(_.name == "C$").get
val clsConstr = convertMethod(cls2.methods.asScala.toList.find(_.name == "<init>").get)
val companionConstr = convertMethod(companion2.methods.asScala.toList.find(_.name == "<init>").get)
assertTrue(clsConstr.localVars.length == 1) // this
assertTrue(companionConstr.localVars.length == 1) // this
}
def assertLocalVarCount(code: String, numVars: Int): Unit = {
assertTrue(singleMethod(dceCompiler)(code).localVars.length == numVars)
}
}
|
