Merge pull request #2214 from JamesIry/master_constant_optimization

Analyze constants to remove unnecessary branches

1 files changed, 27 insertions, 0 deletions

diff --git a/test/files/jvm/constant-optimization/Test.scala b/test/files/jvm/constant-optimization/Test.scala
new file mode 100644
index 0000000000..283aa6f47a
--- /dev/null
+++ b/test/files/jvm/constant-optimization/Test.scala
@@ -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("Foo_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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