Cleanup of constant optimization

This commit cleans up constant optimization from the review of
https://github.com/scala/scala/pull/2214 .

* drops are done using the instruction's consumed count rather than a
  numeric literal
* drops are moved into one common method in the main instruction
  interpreter
* One instance of x.length > y.length is replaced with
  x.lengthCompare(y.length) > 0
* NaN is dealt with by treating it as an UNKNOWN
* A test is added to make sure NaN semantics aren't broken.
* The constant-optmization test is improved with tests for switch
  statements

6 files changed, 118 insertions, 0 deletions

diff --git a/test/files/run/blame_eye_triple_eee.check b/test/files/run/blame_eye_triple_eee.check
new file mode 100644
index 0000000000..5e46d91a8f
--- /dev/null
+++ b/test/files/run/blame_eye_triple_eee.check
@@ -0,0 +1,9 @@
+if (NaN == NaN) is good
+if (x == x) is good
+if (x == NaN) is good
+if (NaN != NaN) is good
+if (x != x) is good
+if (NaN != x) is good
+x matching was good
+NaN matching was good
+loop with NaN was goood
diff --git a/test/files/run/blame_eye_triple_eee.flags b/test/files/run/blame_eye_triple_eee.flags
new file mode 100644
index 0000000000..c9b68d70dc
--- /dev/null
+++ b/test/files/run/blame_eye_triple_eee.flags
@@ -0,0 +1 @@
+-optimise
diff --git a/test/files/run/blame_eye_triple_eee.scala b/test/files/run/blame_eye_triple_eee.scala
new file mode 100644
index 0000000000..1640aead40
--- /dev/null
+++ b/test/files/run/blame_eye_triple_eee.scala
@@ -0,0 +1,61 @@
+object Test extends App {
+  import Double.NaN
+
+  // NaN must not equal NaN no matter what optimizations are applied
+  // All the following will seem redundant, but to an optimizer
+  // they can appear different
+
+  val x = NaN
+
+  if (NaN == NaN)
+    println("if (NaN == NaN) is broken")
+  else
+    println("if (NaN == NaN) is good")
+
+  if (x == x)
+    println("if (x == x) is broken")
+  else
+    println("if (x == x) is good")
+
+  if (x == NaN)
+    println("if (x == NaN) is broken")
+  else
+    println("if (x == NaN) is good")
+
+  if (NaN != NaN)
+    println("if (NaN != NaN) is good")
+  else
+    println("if (NaN != NaN) broken")
+
+  if (x != x)
+    println("if (x != x) is good")
+  else
+    println("if (x != x) broken")
+
+  if (NaN != x)
+    println("if (NaN != x) is good")
+  else
+    println("if (NaN != x) is broken")
+
+  x match {
+    case 0.0d => println("x matched 0!")
+    case NaN => println("x matched NaN!")
+    case _ => println("x matching was good")
+  }
+
+  NaN match {
+    case 0.0d => println("NaN matched 0!")
+    case NaN => println("NaN matched NaN!")
+    case _ => println("NaN matching was good")
+  }
+
+  var z = 0.0d
+  var i = 0
+  while (i < 10) {
+    if (i % 2 == 0) z = NaN
+    else z = NaN
+    i += 1
+  }
+  if (z.isNaN && i == 10) println("loop with NaN was goood")
+  else println("loop with NaN was broken")
+}
diff --git a/test/files/run/constant-optimization.check b/test/files/run/constant-optimization.check
index 090e53ac40..957ffc5a87 100644
--- a/test/files/run/constant-optimization.check
+++ b/test/files/run/constant-optimization.check
@@ -1,2 +1,5 @@
 testBothReachable: good
 testOneReachable: good
+testAllReachable: good
+testOneUnreachable: good
+testDefaultUnreachable: good
diff --git a/test/files/run/constant-optimization.flags b/test/files/run/constant-optimization.flags
new file mode 100644
index 0000000000..c9b68d70dc
--- /dev/null
+++ b/test/files/run/constant-optimization.flags
@@ -0,0 +1 @@
+-optimise
diff --git a/test/files/run/constant-optimization.scala b/test/files/run/constant-optimization.scala
index 86f981e13f..5d13272f3b 100644
--- a/test/files/run/constant-optimization.scala
+++ b/test/files/run/constant-optimization.scala
@@ -13,6 +13,49 @@ object Test extends App {
     println(s"testOneReachable: $y")
   }
 
+  def testAllReachable() {
+    val i = util.Random.nextInt
+    val y = (i % 2) match {
+      case 0 => "good"
+      case 1 => "good"
+      case _ => "good"
+    }
+    println(s"testAllReachable: $y")
+  }
+
+  def testOneUnreachable() {
+    val i = util.Random.nextInt
+    val x = if (i % 2 == 0) {
+      1
+    } else {
+      2
+    }
+    val y = x match {
+      case 0 => "good"
+      case 1 => "good"
+      case _ => "good"
+    }
+    println(s"testOneUnreachable: $y")
+  }
+
+  def testDefaultUnreachable() {
+    val i = util.Random.nextInt
+    val x = if (i % 2 == 0) {
+      1
+    } else {
+      2
+    }
+    val y = x match {
+      case 1 => "good"
+      case 2 => "good"
+      case _ => "good"
+    }
+    println(s"testDefaultUnreachable: $y")
+  }
+
   testBothReachable()
   testOneReachable()
+  testAllReachable()
+  testOneUnreachable()
+  testDefaultUnreachable()
 }