Improve GVN handling of ElementTransitions.

test/mjsunit/elements-transition-hoisting.js

+// Copyright 2011 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Flags: --allow-natives-syntax --smi-only-arrays
+
+// Ensure that ElementsKind transitions in various situations are hoisted (or
+// not hoisted) correctly, don't change the semantics programs and don't trigger
+// deopt through hoisting in important situations.
+
+support_smi_only_arrays = %HasFastSmiOnlyElements(new Array(1,2,3,4,5,6));
+
+if (support_smi_only_arrays) {
+  print("Tests include smi-only arrays.");
+} else {
+  print("Tests do NOT include smi-only arrays.");
+}
+
+if (support_smi_only_arrays) {
+  // Make sure that a simple elements array transitions inside a loop before
+  // stores to an array gets hoisted in a way that doesn't generate a deopt in
+  // simple cases.}
+  function testDoubleConversion4(a) {
+    var object = new Object();
+    a[0] = 0;
+    var count = 3;
+    do {
+      a[0] = object;
+    } while (--count > 0);
+  }
+
+  testDoubleConversion4(new Array(5));
+  %OptimizeFunctionOnNextCall(testDoubleConversion4);
+  testDoubleConversion4(new Array(5));
+  testDoubleConversion4(new Array(5));
+  assertTrue(2 != %GetOptimizationStatus(testDoubleConversion4));
+
+  // Make sure that non-element related map checks that are not preceded by
+  // transitions in a loop still get hoisted in a way that doesn't generate a
+  // deopt in simple cases.
+  function testExactMapHoisting(a) {
+    var object = new Object();
+    a.foo = 0;
+    a[0] = 0;
+    a[1] = 1;
+    var count = 3;
+    do {
+      a.foo = object; // This map check should be hoistable
+      a[1] = object;
+      result = a.foo == object && a[1] == object;
+    } while (--count > 0);
+  }
+
+  testExactMapHoisting(new Array(5));
+  %OptimizeFunctionOnNextCall(testExactMapHoisting);
+  testExactMapHoisting(new Array(5));
+  testExactMapHoisting(new Array(5));
+  assertTrue(2 != %GetOptimizationStatus(testExactMapHoisting));
+
+  // Make sure that non-element related map checks do NOT get hoisted if they
+  // depend on an elements transition before them  and it's not possible to hoist

[fschneider, 2012/02/09 08:43:32]

Long line.

+  // that transition.
+  function testExactMapHoisting2(a) {
+    var object = new Object();
+    a.foo = 0;
+    a[0] = 0;
+    a[1] = 1;
+    var count = 3;
+    do {
+      if (a.bar === undefined) {
+        a[1] = 2.5;
+      }
+      a.foo = object; // This map check should NOT be hoistable because it
+                      // includes a check for the FAST_ELEMENTS map as well as
+                      // the FAST_DOUBLE_ELEMENTS map, which depends on the
+                      // double transition above in the if, which cannot be
+                      // hoisted.
+    } while (--count > 0);
+  }
+
+  testExactMapHoisting2(new Array(5));
+  %OptimizeFunctionOnNextCall(testExactMapHoisting2);
+  testExactMapHoisting2(new Array(5));
+  testExactMapHoisting2(new Array(5));
+  assertTrue(2 != %GetOptimizationStatus(testExactMapHoisting2));
+
+  // Make sure that non-element related map checks do get hoisted if they use
+  // the transitioned map for the check and all transitions that they depend
+  // upon can hoisted, too.
+  function testExactMapHoisting3(a) {
+    var object = new Object();
+    a.foo = 0;
+    a[0] = 0;
+    a[1] = 1;
+    var count = 3;
+    do {
+      a[1] = 2.5;
+      a.foo = object; // This map check should be hoistable because all elements
+                      // transitions in the loop can also be hoisted.
+    } while (--count > 0);
+  }
+
+  var add_transition = new Array(5);
+  add_transition.foo = 0;
+  add_transition[0] = new Object(); // For FAST_ELEMENT transition to be created
+  testExactMapHoisting3(new Array(5));
+  %OptimizeFunctionOnNextCall(testExactMapHoisting3);
+  testExactMapHoisting3(new Array(5));
+  testExactMapHoisting3(new Array(5));
+  assertTrue(2 != %GetOptimizationStatus(testExactMapHoisting3));
+
+  function testDominatingTransitionHoisting1(a) {
+    var object = new Object();
+    a[0] = 0;
+    var count = 3;
+    do {
+      if (a.baz != true) {
+        a[1] = 2.5;
+      }
+      a[0] = object;
+    } while (--count > 3);
+  }
+
+  testDominatingTransitionHoisting1(new Array(5));
+  %OptimizeFunctionOnNextCall(testDominatingTransitionHoisting1);
+  testDominatingTransitionHoisting1(new Array(5));
+  testDominatingTransitionHoisting1(new Array(5));
+  assertTrue(2 != %GetOptimizationStatus(testDominatingTransitionHoisting1));
+
+  function testHoistingWithSideEffect(a) {
+    var object = new Object();
+    a[0] = 0;
+    var count = 3;
+    do {
+      assertTrue(true);
+      a[0] = object;
+    } while (--count > 3);
+  }
+
+  testHoistingWithSideEffect(new Array(5));
+  %OptimizeFunctionOnNextCall(testHoistingWithSideEffect);
+  testHoistingWithSideEffect(new Array(5));
+  testHoistingWithSideEffect(new Array(5));
+  assertTrue(2 != %GetOptimizationStatus(testHoistingWithSideEffect));
+}