Merge pull request #2214 from JamesIry/master_constant_optimization

Analyze constants to remove unnecessary branches

13 files changed, 192 insertions, 13 deletions

diff --git a/test/files/jvm/constant-optimization/Foo_1.flags b/test/files/jvm/constant-optimization/Foo_1.flags
new file mode 100644
index 0000000000..86f52af447
--- /dev/null
+++ b/test/files/jvm/constant-optimization/Foo_1.flags
@@ -0,0 +1 @@
+-Ynooptimise -Yconst-opt
\ No newline at end of file
diff --git a/test/files/jvm/constant-optimization/Foo_1.scala b/test/files/jvm/constant-optimization/Foo_1.scala
new file mode 100644
index 0000000000..cb67ad4e90
--- /dev/null
+++ b/test/files/jvm/constant-optimization/Foo_1.scala
@@ -0,0 +1,9 @@
+class Foo_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)
+  }
+}
\ No newline at end of file
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
+  }
+}
\ No newline at end of file
diff --git a/test/files/neg/t6446-additional.check b/test/files/neg/t6446-additional.check
index 53dd383941..24201c07c2 100755
--- a/test/files/neg/t6446-additional.check
+++ b/test/files/neg/t6446-additional.check
@@ -25,7 +25,8 @@ superaccessors   6  add super accessors in traits and nested classes
        inliner  23  optimization: do inlining
 inlinehandlers  24  optimization: inline exception handlers
       closelim  25  optimization: eliminate uncalled closures
-           dce  26  optimization: eliminate dead code
-           jvm  27  generate JVM bytecode
-       ploogin  28  A sample phase that does so many things it's kind of hard...
-      terminal  29  The last phase in the compiler chain
+      constopt  26  optimization: optimize null and other constants
+           dce  27  optimization: eliminate dead code
+           jvm  28  generate JVM bytecode
+       ploogin  29  A sample phase that does so many things it's kind of hard...
+      terminal  30  The last phase in the compiler chain
diff --git a/test/files/neg/t6446-missing.check b/test/files/neg/t6446-missing.check
index f976bf480e..6e5bdcf07c 100755
--- a/test/files/neg/t6446-missing.check
+++ b/test/files/neg/t6446-missing.check
@@ -26,6 +26,7 @@ superaccessors   6  add super accessors in traits and nested classes
        inliner  23  optimization: do inlining
 inlinehandlers  24  optimization: inline exception handlers
       closelim  25  optimization: eliminate uncalled closures
-           dce  26  optimization: eliminate dead code
-           jvm  27  generate JVM bytecode
-      terminal  28  The last phase in the compiler chain
+      constopt  26  optimization: optimize null and other constants
+           dce  27  optimization: eliminate dead code
+           jvm  28  generate JVM bytecode
+      terminal  29  The last phase in the compiler chain
diff --git a/test/files/neg/t6446-show-phases.check b/test/files/neg/t6446-show-phases.check
index 5bbe43990c..a1bf408506 100644
--- a/test/files/neg/t6446-show-phases.check
+++ b/test/files/neg/t6446-show-phases.check
@@ -25,6 +25,7 @@ superaccessors   6  add super accessors in traits and nested classes
        inliner  23  optimization: do inlining
 inlinehandlers  24  optimization: inline exception handlers
       closelim  25  optimization: eliminate uncalled closures
-           dce  26  optimization: eliminate dead code
-           jvm  27  generate JVM bytecode
-      terminal  28  The last phase in the compiler chain
+      constopt  26  optimization: optimize null and other constants
+           dce  27  optimization: eliminate dead code
+           jvm  28  generate JVM bytecode
+      terminal  29  The last phase in the compiler chain
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
new file mode 100644
index 0000000000..957ffc5a87
--- /dev/null
+++ b/test/files/run/constant-optimization.check
@@ -0,0 +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
new file mode 100644
index 0000000000..5d13272f3b
--- /dev/null
+++ b/test/files/run/constant-optimization.scala
@@ -0,0 +1,61 @@
+object Test extends App {
+  def testBothReachable() {
+    val i = util.Random.nextInt
+    val x = if (i % 2 == 0) null else "good"
+    val y = if (x == null) "good" else x + ""
+    println(s"testBothReachable: $y")
+  }
+
+  def testOneReachable() {
+    val i = 1
+    val x = if (i != 1) null else "good"
+    val y = if (x == null) "good" else x + ""
+    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()
+}
diff --git a/test/files/run/programmatic-main.check b/test/files/run/programmatic-main.check
index d472c569d2..61b947214c 100644
--- a/test/files/run/programmatic-main.check
+++ b/test/files/run/programmatic-main.check
@@ -25,7 +25,8 @@ superaccessors   6  add super accessors in traits and nested classes
        inliner  23  optimization: do inlining
 inlinehandlers  24  optimization: inline exception handlers
       closelim  25  optimization: eliminate uncalled closures
-           dce  26  optimization: eliminate dead code
-           jvm  27  generate JVM bytecode
-      terminal  28  The last phase in the compiler chain
+      constopt  26  optimization: optimize null and other constants
+           dce  27  optimization: eliminate dead code
+           jvm  28  generate JVM bytecode
+      terminal  29  The last phase in the compiler chain