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package scala.tools.nsc
package backend.jvm
package opt
import org.junit.Assert._
import org.junit.Test
import org.junit.runner.RunWith
import org.junit.runners.JUnit4
import scala.tools.asm.Opcodes._
import scala.tools.partest.ASMConverters
import scala.tools.partest.ASMConverters._
import scala.tools.testing.BytecodeTesting._
@RunWith(classOf[JUnit4])
class SimplifyJumpsTest {
@Test
def simpleGotoReturn(): Unit = {
val ops = List(
Jump(GOTO, Label(2)), // replaced by RETURN
Op(ICONST_1), // need some code, otherwise removeJumpToSuccessor kicks in
Op(POP),
Label(1), // multiple labels OK
Label(2),
Label(3),
Op(RETURN)
)
val method = genMethod()(ops: _*)
assertTrue(LocalOptImpls.simplifyJumps(method))
assertSameCode(instructionsFromMethod(method), Op(RETURN) :: ops.tail)
}
@Test
def simpleGotoThrow(): Unit = {
val rest = List(
Op(ICONST_1), // need some code, otherwise removeJumpToSuccessor kicks in
Op(POP),
Label(1),
Label(2),
Label(3),
Op(ATHROW)
)
val method = genMethod()(
Op(ACONST_NULL) ::
Jump(GOTO, Label(2)) :: // replaced by ATHROW
rest: _*
)
assertTrue(LocalOptImpls.simplifyJumps(method))
assertSameCode(instructionsFromMethod(method), Op(ACONST_NULL) :: Op(ATHROW) :: rest)
}
@Test
def gotoThrowInTry(): Unit = {
val handler = List(ExceptionHandler(Label(1), Label(2), Label(4), Some("java/lang/Throwable")))
val initialInstrs = List(
Label(1),
Op(ACONST_NULL),
Jump(GOTO, Label(3)), // not by ATHROW (would move the ATHROW into a try block)
Label(2),
Op(ICONST_1), // need some code, otherwise removeJumpToSuccessor kicks in
Op(POP),
Label(3),
Op(ATHROW),
Label(4),
Op(POP),
Op(RETURN)
)
val method = genMethod(handlers = handler)(initialInstrs: _*)
assertFalse(LocalOptImpls.simplifyJumps(method))
assertSameCode(instructionsFromMethod(method), initialInstrs)
val optMethod = genMethod()(initialInstrs: _*) // no handler
assertTrue(LocalOptImpls.simplifyJumps(optMethod))
assertSameCode(instructionsFromMethod(optMethod).take(3), List(Label(1), Op(ACONST_NULL), Op(ATHROW)))
}
@Test
def simplifyBranchOverGoto(): Unit = {
val begin = List(
VarOp(ILOAD, 1),
Jump(IFGE, Label(2))
)
val rest = List(
Jump(GOTO, Label(3)),
Label(11), // other labels here are allowed
Label(2),
VarOp(ILOAD, 1),
Op(RETURN),
Label(3),
VarOp(ILOAD, 1),
Op(IRETURN)
)
val method = genMethod()(begin ::: rest: _*)
assertTrue(LocalOptImpls.simplifyJumps(method))
assertSameCode(
instructionsFromMethod(method),
List(VarOp(ILOAD, 1), Jump(IFLT, Label(3))) ::: rest.tail )
// branch over goto is OK even if there's a label in between, if that label is not a jump target
val withNonJumpTargetLabel = genMethod()(begin ::: Label(22) :: rest: _*)
assertTrue(LocalOptImpls.simplifyJumps(withNonJumpTargetLabel))
assertSameCode(
instructionsFromMethod(withNonJumpTargetLabel),
List(VarOp(ILOAD, 1), Jump(IFLT, Label(3)), Label(22)) ::: rest.tail )
// if the Label(22) between IFGE and GOTO is the target of some jump, we cannot rewrite the IFGE
// and remove the GOTO: removing the GOTO would change semantics. However, the jump that targets
// Label(22) will be re-written (jump-chain collapsing), so in a second round, the IFGE is still
// rewritten to IFLT
val twoRounds = genMethod()(List(VarOp(ILOAD, 1), Jump(IFLE, Label(22))) ::: begin ::: Label(22) :: rest: _*)
assertTrue(LocalOptImpls.simplifyJumps(twoRounds))
assertSameCode(
instructionsFromMethod(twoRounds),
List(VarOp(ILOAD, 1), Jump(IFLE, Label(3)), VarOp(ILOAD, 1), Jump(IFLT, Label(3)), Label(22)) ::: rest.tail )
}
@Test
def ensureGotoRemoved(): Unit = {
def code(jumps: Instruction*) = List(
VarOp(ILOAD, 1)) ::: jumps.toList ::: List(
Label(2),
Op(RETURN),
Label(3),
Op(RETURN)
)
// ensures that the goto is safely removed. ASM supports removing while iterating, but not the
// next element of the current. Here, the current is the IFGE, the next is the GOTO.
val method = genMethod()(code(Jump(IFGE, Label(2)), Jump(GOTO, Label(3))): _*)
assertTrue(LocalOptImpls.simplifyJumps(method))
assertSameCode(instructionsFromMethod(method), code(Jump(IFLT, Label(3))))
}
@Test
def removeJumpToSuccessor(): Unit = {
val ops = List(
Jump(GOTO, Label(1)),
Label(11),
Label(1),
Label(2),
VarOp(ILOAD, 1),
Op(IRETURN)
)
val method = genMethod()(ops: _*)
assertTrue(LocalOptImpls.simplifyJumps(method))
assertSameCode(instructionsFromMethod(method), ops.tail)
}
@Test
def collapseJumpChains(): Unit = {
def ops(target1: Int, target2: Int, target3: Int) = List(
VarOp(ILOAD, 1),
Jump(IFGE, Label(target1)), // initially 1, then 3
VarOp(ILOAD, 1),
Op(IRETURN),
Label(2),
Jump(GOTO, Label(target3)),
Label(1),
Jump(GOTO, Label(target2)), // initially 2, then 3
VarOp(ILOAD, 1), // some code to prevent jumpToSuccessor optimization (once target2 is replaced by 3)
Op(RETURN),
Label(3),
VarOp(ILOAD, 1),
Op(IRETURN)
)
val method = genMethod()(ops(1, 2, 3): _*)
assertTrue(LocalOptImpls.simplifyJumps(method))
assertSameCode(instructionsFromMethod(method), ops(3, 3, 3))
}
@Test
def collapseJumpChainLoop(): Unit = {
def ops(target: Int) = List(
VarOp(ILOAD, 1),
Jump(IFGE, Label(target)),
VarOp(ILOAD, 1), // some code to prevent rewriting the conditional jump
Op(IRETURN),
Label(4),
Jump(GOTO, Label(3)),
VarOp(ILOAD, 1), // some code to prevent jumpToSuccessor (label 3)
Op(IRETURN),
Label(3),
Jump(GOTO, Label(4)),
Label(2),
Jump(GOTO, Label(3))
)
val method = genMethod()(ops(2): _*)
assertTrue(LocalOptImpls.simplifyJumps(method))
assertSameCode(instructionsFromMethod(method), ops(3))
}
@Test
def simplifyThenElseSameTarget(): Unit = {
def ops(jumpOp: Instruction) = List(
VarOp(ILOAD, 1),
jumpOp,
Label(2),
Jump(GOTO, Label(1)),
VarOp(ILOAD, 1), // some code to prevent jumpToSuccessor (label 1)
Op(IRETURN),
Label(1),
VarOp(ILOAD, 1),
Op(IRETURN)
)
val method = genMethod()(ops(Jump(IFGE, Label(1))): _*)
assertTrue(LocalOptImpls.simplifyJumps(method))
assertSameCode(instructionsFromMethod(method), ops(Op(POP)))
}
@Test
def thenElseSameTargetLoop(): Unit = {
def ops(br: List[Instruction]) = List(
VarOp(ILOAD, 1),
VarOp(ILOAD, 2)) ::: br ::: List(
Label(1),
Jump(GOTO, Label(1))
)
val method = genMethod()(ops(List(Jump(IF_ICMPGE, Label(1)))): _*)
assertTrue(LocalOptImpls.simplifyJumps(method))
assertSameCode(instructionsFromMethod(method), ops(List(Op(POP), Op(POP))))
}
}
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