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BCodeOpt: test constant folding including nullness propagation

A test is added to verify branches are removed when their outcome
can be determined at compile time based on constant-folding and
nullness propagation.

The test is the BCodeOpt counterpart to the jvm test introduced in
commit 69109c0
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magarciaEPFL committed May 29, 2013
1 parent 435b133 commit 3281236219ad0a7894a0c1c743e8550e2ce20dbf
@@ -0,0 +1 @@
-neo:o1 -Ynooptimize
@@ -0,0 +1,11 @@
class CF_1 {
def foo() {
// constant optimization should eliminate all branches
val i = 1
val x = if (i != 1) null else "good"
val y = if (x == null) "good" else x + ""
println(y)
}
}
@@ -0,0 +1,27 @@
import scala.tools.partest.BytecodeTest
import scala.tools.asm
import asm.tree.InsnList
import scala.collection.JavaConverters._
object Test extends BytecodeTest {
val comparisons = Set(asm.Opcodes.IF_ACMPEQ, asm.Opcodes.IF_ACMPNE, asm.Opcodes.IF_ICMPEQ, asm.Opcodes.IF_ICMPGE, asm.Opcodes.IF_ICMPGT, asm.Opcodes.IF_ICMPLE,
asm.Opcodes.IF_ICMPLT, asm.Opcodes.IF_ICMPNE, asm.Opcodes.IFEQ, asm.Opcodes.IFGE, asm.Opcodes.IFGT, asm.Opcodes.IFLE, asm.Opcodes.IFLT,
asm.Opcodes.IFNE, asm.Opcodes.IFNONNULL, asm.Opcodes.IFNULL)
def show: Unit = {
val classNode = loadClassNode("CF_1")
val methodNode = getMethod(classNode, "foo")
// after optimization there should be no comparisons left
val expected = 0
val got = countComparisons(methodNode.instructions)
assert(got == expected, s"expected $expected but got $got comparisons")
}
def countComparisons(insnList: InsnList): Int = {
def isComparison(node: asm.tree.AbstractInsnNode): Boolean =
(comparisons contains node.getOpcode)
insnList.iterator.asScala count isComparison
}
}

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