Elements load depends on the type of the receiver.

R=jkummerow@chromium.org

Review URL: https://chromiumcodereview.appspot.com/10918005

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@12413 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/hydrogen-instructions.h

@@ -2068,14 +2068,18 @@ class HUnaryMathOperation: public HTemplateInstruction<2> {
 };
 
 
-class HLoadElements: public HUnaryOperation {
+class HLoadElements: public HTemplateInstruction<2> {
  public:
-  explicit HLoadElements(HValue* value) : HUnaryOperation(value) {
+  HLoadElements(HValue* value, HValue* typecheck) {
+    SetOperandAt(0, value);
+    SetOperandAt(1, typecheck);
     set_representation(Representation::Tagged());
     SetFlag(kUseGVN);
     SetGVNFlag(kDependsOnElementsPointer);
   }
 
+  HValue* value() { return OperandAt(0); }
+
   virtual Representation RequiredInputRepresentation(int index) {
     return Representation::Tagged();
   }

src/hydrogen.cc

@@ -5218,7 +5218,9 @@ void HGraphBuilder::VisitArrayLiteral(ArrayLiteral* expr) {
     HValue* value = Pop();
     if (!Smi::IsValid(i)) return Bailout("Non-smi key in array literal");
 
-    elements = new(zone()) HLoadElements(literal);
+    // Pass in literal as dummy depedency, since  the receiver always has
+    // elements.
+    elements = new(zone()) HLoadElements(literal, literal);
     AddInstruction(elements);
 
     HValue* key = AddInstruction(
@@ -6186,7 +6188,8 @@ HInstruction* HGraphBuilder::BuildUncheckedMonomorphicElementAccess(
   }
   bool fast_smi_only_elements = map->has_fast_smi_elements();
   bool fast_elements = map->has_fast_object_elements();
-  HInstruction* elements = AddInstruction(new(zone()) HLoadElements(object));
+  HInstruction* elements = 
+      AddInstruction(new(zone()) HLoadElements(object, mapcheck));
   if (is_store && (fast_elements || fast_smi_only_elements)) {
     HCheckMaps* check_cow_map = new(zone()) HCheckMaps(
         elements, isolate()->factory()->fixed_array_map(), zone());
@@ -6366,13 +6369,15 @@ HValue* HGraphBuilder::HandlePolymorphicElementAccess(HValue* object,
     return is_store ? NULL : instr;
   }
 
-  AddInstruction(HCheckInstanceType::NewIsSpecObject(object, zone()));
+  HInstruction* checkspec =
+      AddInstruction(HCheckInstanceType::NewIsSpecObject(object, zone()));
   HBasicBlock* join = graph()->CreateBasicBlock();
 
   HInstruction* elements_kind_instr =
       AddInstruction(new(zone()) HElementsKind(object));
   HCompareConstantEqAndBranch* elements_kind_branch = NULL;
-  HInstruction* elements = AddInstruction(new(zone()) HLoadElements(object));
+  HInstruction* elements =
+      AddInstruction(new(zone()) HLoadElements(object, checkspec));
   HLoadExternalArrayPointer* external_elements = NULL;
   HInstruction* checked_key = NULL;
 

test/mjsunit/regress/regress-load-elements.js

+// Copyright 2012 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
+
+function bad_func(o,a) {
+  for (var i = 0; i < 1; ++i) {
+    o.prop = 0;
+    var x = a[0];
+  }
+}
+
+o = new Object();
+a = {};
+a[0] = 1;
+bad_func(o, a);
+
+o = new Object();
+bad_func(o, a);
+
+// Optimize. Before the fix, the elements-load and subsequent fixed-array-length
+// were hoisted above the map check. This is invalid since not all types
+// necessarily have elements.
+%OptimizeFunctionOnNextCall(bad_func);
+bad_func(o, "");