Merge pull request #2001 from JamesIry/2.10.x_SI-5313

SI-5313 Do not eliminate stores that potentially wipe referenes

2 files changed, 66 insertions, 0 deletions

diff --git a/test/files/run/t5313.check b/test/files/run/t5313.check
new file mode 100644
index 0000000000..7a48b2b711
--- /dev/null
+++ b/test/files/run/t5313.check
@@ -0,0 +1,12 @@
+STORE_LOCAL(variable kept1)
+STORE_LOCAL(value result)
+STORE_LOCAL(variable kept1)
+STORE_LOCAL(variable kept2)
+STORE_LOCAL(value kept3)
+STORE_LOCAL(variable kept2)
+STORE_LOCAL(variable kept4)
+STORE_LOCAL(variable kept4)
+STORE_LOCAL(variable kept5)
+STORE_LOCAL(variable kept5)
+STORE_LOCAL(variable kept6)
+STORE_LOCAL(variable kept6)
diff --git a/test/files/run/t5313.scala b/test/files/run/t5313.scala
new file mode 100644
index 0000000000..7da8726a1f
--- /dev/null
+++ b/test/files/run/t5313.scala
@@ -0,0 +1,54 @@
+import scala.tools.partest.IcodeTest
+
+object Test extends IcodeTest {
+  override def printIcodeAfterPhase = "dce"
+
+  override def extraSettings: String = super.extraSettings + " -optimize"  
+
+  override def code =
+    """class Foo {
+      def randomBoolean = util.Random.nextInt % 2 == 0
+      def bar = {
+        var kept1 = new Object
+        val result = new java.lang.ref.WeakReference(kept1)
+        kept1 = null // we can't eliminate this assigment because result can observe
+                   // when the object has no more references. See SI-5313
+        kept1 = new Object // but we can eliminate this one because kept1 has already been clobbered
+        var erased2 = null // we can eliminate this store because it's never used
+        val erased3 = erased2 // and this
+        var erased4 = erased2 // and this
+        val erased5 = erased4 // and this
+        var kept2: Object = new Object // ultimately can't be eliminated 
+        while(randomBoolean) {
+          val kept3 = kept2
+          kept2 = null // this can't, because it clobbers kept2, which is used
+          erased4 = null // safe to eliminate       
+          println(kept3)
+        }
+        var kept4 = new Object // have to keep, it's used
+        try
+          println(kept4)
+        catch {
+          case _ : Throwable => kept4 = null // have to keep, it clobbers kept4 which is used
+        }
+        var kept5 = new Object
+        print(kept5)
+        kept5 = null // can't eliminate it's a clobber and it's used
+        print(kept5)
+        kept5 = null // can eliminate because we don't care about clobbers of nulls
+        while(randomBoolean) {
+          var kept6: AnyRef = null // not used, but have to keep because it clobbers the next used store
+                                   // on the back edge of the loop
+          kept6 = new Object // used
+          println(kept6)
+        }
+        result
+      }
+    }""".stripMargin
+
+  override def show() {
+    val storeLocal = "STORE_LOCAL"
+    val lines1 = collectIcode("") filter (_ contains storeLocal) map (x => x.drop(x.indexOf(storeLocal)))
+    println(lines1 mkString "\n")
+  }
+}