GVN fix, preventing loads hoisting above stores to the same field when HObjectAccess...

R=bmeurer@chromium.org

Review URL: https://codereview.chromium.org/331493006

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@21830 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

diff --git a/src/hydrogen-gvn.cc b/src/hydrogen-gvn.cc
index e6f1ae9..385947d 100644 (file)
--- a/src/hydrogen-gvn.cc
+++ b/src/hydrogen-gvn.cc
@@ -466,7 +466,7 @@ bool SideEffectsTracker::ComputeGlobalVar(Unique<Cell> cell, int* index) {
 bool SideEffectsTracker::ComputeInobjectField(HObjectAccess access,
                                               int* index) {
   for (int i = 0; i < num_inobject_fields_; ++i) {
-    if (access.Equals(inobject_fields_[i])) {
+    if (access.SameField(inobject_fields_[i])) {
       *index = i;
       return true;
     }

diff --git a/src/hydrogen-instructions.h b/src/hydrogen-instructions.h
index f1720f4..fce5d68 100644 (file)
--- a/src/hydrogen-instructions.h
+++ b/src/hydrogen-instructions.h
@@ -6202,7 +6202,14 @@ class HObjectAccess V8_FINAL {
   void PrintTo(StringStream* stream) const;
 
   inline bool Equals(HObjectAccess that) const {
-    return value_ == that.value_;  // portion and offset must match
+    return value_ == that.value_;
+  }
+
+  // Returns true if |this| access refers to the same field as |that|, which
+  // means that both have same |offset| and |portion| values.
+  inline bool SameField(HObjectAccess that) const {
+    uint32_t mask = PortionField::kMask | OffsetField::kMask;
+    return (value_ & mask) == (that.value_ & mask);
   }
 
  protected:

diff --git a/test/mjsunit/regress/regress-gvn-ftt.js b/test/mjsunit/regress/regress-gvn-ftt.js
new file mode 100644 (file)
index 0000000..d2cb443
--- /dev/null
+++ b/test/mjsunit/regress/regress-gvn-ftt.js
@@ -0,0 +1,27 @@
+// Copyright 2014 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Flags: --allow-natives-syntax --track-field-types --use-gvn
+
+function A(id) {
+  this.id = id;
+}
+
+var a1 = new A(1);
+var a2 = new A(2);
+
+
+var g;
+function f(o, value) {
+  g = o.o;
+  o.o = value;
+  return o.o;
+}
+
+var obj = {o: a1};
+
+f(obj, a1);
+f(obj, a1);
+%OptimizeFunctionOnNextCall(f);
+assertEquals(a2.id, f(obj, a2).id);