Add and use ElementsKind side effect

Also partition side effects into observable and not observable, with only observable requiring Simulates and non-observable changes able to participate in GVN and code hoisting.

BUG=none
TEST=none

Review URL: http://codereview.chromium.org/8380017

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@9847 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/arm/lithium-arm.cc

@@ -750,7 +750,7 @@ LInstruction* LChunkBuilder::MarkAsCall(LInstruction* instr,
   instr->MarkAsCall();
   instr = AssignPointerMap(instr);
 
-  if (hinstr->HasSideEffects()) {
+  if (hinstr->HasObservableSideEffects()) {
     ASSERT(hinstr->next()->IsSimulate());
     HSimulate* sim = HSimulate::cast(hinstr->next());
     instr = SetInstructionPendingDeoptimizationEnvironment(
@@ -762,7 +762,8 @@ LInstruction* LChunkBuilder::MarkAsCall(LInstruction* instr,
   // Thus we still need to attach environment to this call even if
   // call sequence can not deoptimize eagerly.
   bool needs_environment =
-      (can_deoptimize == CAN_DEOPTIMIZE_EAGERLY) || !hinstr->HasSideEffects();
+      (can_deoptimize == CAN_DEOPTIMIZE_EAGERLY) ||
+      !hinstr->HasObservableSideEffects();
   if (needs_environment && !instr->HasEnvironment()) {
     instr = AssignEnvironment(instr);
   }

src/hydrogen-instructions.cc

@@ -564,7 +564,7 @@ void HInstruction::InsertAfter(HInstruction* previous) {
   // followed by a simulate instruction, we need to insert after the
   // simulate instruction instead.
   HInstruction* next = previous->next_;
-  if (previous->HasSideEffects() && next != NULL) {
+  if (previous->HasObservableSideEffects() && next != NULL) {
     ASSERT(next->IsSimulate());
     previous = next;
     next = previous->next_;
@@ -604,7 +604,7 @@ void HInstruction::Verify() {
 
   // Verify that instructions that may have side-effects are followed
   // by a simulate instruction.
-  if (HasSideEffects() && !IsOsrEntry()) {
+  if (HasObservableSideEffects() && !IsOsrEntry()) {
     ASSERT(next()->IsSimulate());
   }
 

src/hydrogen-instructions.h

@@ -181,6 +181,7 @@ class LChunkBuilder;
   V(Calls)                                     \
   V(InobjectFields)                            \
   V(BackingStoreFields)                        \
+  V(ElementsKind)                              \
   V(ArrayElements)                             \
   V(DoubleArrayElements)                       \
   V(SpecializedArrayElements)                  \
@@ -619,8 +620,14 @@ class HValue: public ZoneObject {
   void SetAllSideEffects() { flags_ |= AllSideEffects(); }
   void ClearAllSideEffects() { flags_ &= ~AllSideEffects(); }
   bool HasSideEffects() const { return (flags_ & AllSideEffects()) != 0; }
+  bool HasObservableSideEffects() const {
+    return (flags_ & ObservableSideEffects()) != 0;
+  }
 
   int ChangesFlags() const { return flags_ & ChangesFlagsMask(); }
+  int ObservableChangesFlags() const {
+    return flags_ & ChangesFlagsMask() & ObservableSideEffects();
+  }
 
   Range* range() const { return range_; }
   bool HasRange() const { return range_ != NULL; }
@@ -700,6 +707,12 @@ class HValue: public ZoneObject {
     return ChangesFlagsMask() & ~(1 << kChangesOsrEntries);
   }
 
+  // A flag mask of all side effects that can make observable changes in
+  // an executing program (i.e. are not safe to repeat, move or remove);
+  static int ObservableSideEffects() {
+    return ChangesFlagsMask() & ~(1 << kChangesElementsKind);
+  }
+
   // Remove the matching use from the use list if present.  Returns the
   // removed list node or NULL.
   HUseListNode* RemoveUse(HValue* value, int index);
@@ -1737,7 +1750,7 @@ class HElementsKind: public HUnaryOperation {
   explicit HElementsKind(HValue* value) : HUnaryOperation(value) {
     set_representation(Representation::Integer32());
     SetFlag(kUseGVN);
-    SetFlag(kDependsOnMaps);
+    SetFlag(kDependsOnElementsKind);
   }
 
   virtual Representation RequiredInputRepresentation(int index) {
@@ -1864,6 +1877,7 @@ class HLoadElements: public HUnaryOperation {
     set_representation(Representation::Tagged());
     SetFlag(kUseGVN);
     SetFlag(kDependsOnMaps);
+    SetFlag(kDependsOnElementsKind);
   }
 
   virtual Representation RequiredInputRepresentation(int index) {
@@ -3886,7 +3900,7 @@ class HTransitionElementsKind: public HTemplateInstruction<1> {
         transitioned_map_(transitioned_map) {
     SetOperandAt(0, object);
     SetFlag(kUseGVN);
-    SetFlag(kDependsOnMaps);
+    SetFlag(kChangesElementsKind);
     set_representation(Representation::Tagged());
   }
 

src/ia32/lithium-ia32.cc

@@ -750,7 +750,7 @@ LInstruction* LChunkBuilder::MarkAsCall(LInstruction* instr,
   instr->MarkAsCall();
   instr = AssignPointerMap(instr);
 
-  if (hinstr->HasSideEffects()) {
+  if (hinstr->HasObservableSideEffects()) {
     ASSERT(hinstr->next()->IsSimulate());
     HSimulate* sim = HSimulate::cast(hinstr->next());
     instr = SetInstructionPendingDeoptimizationEnvironment(
@@ -762,7 +762,8 @@ LInstruction* LChunkBuilder::MarkAsCall(LInstruction* instr,
   // Thus we still need to attach environment to this call even if
   // call sequence can not deoptimize eagerly.
   bool needs_environment =
-      (can_deoptimize == CAN_DEOPTIMIZE_EAGERLY) || !hinstr->HasSideEffects();
+      (can_deoptimize == CAN_DEOPTIMIZE_EAGERLY) ||
+      !hinstr->HasObservableSideEffects();
   if (needs_environment && !instr->HasEnvironment()) {
     instr = AssignEnvironment(instr);
   }

src/x64/lithium-x64.cc

@@ -745,7 +745,7 @@ LInstruction* LChunkBuilder::MarkAsCall(LInstruction* instr,
   instr->MarkAsCall();
   instr = AssignPointerMap(instr);
 
-  if (hinstr->HasSideEffects()) {
+  if (hinstr->HasObservableSideEffects()) {
     ASSERT(hinstr->next()->IsSimulate());
     HSimulate* sim = HSimulate::cast(hinstr->next());
     instr = SetInstructionPendingDeoptimizationEnvironment(
@@ -757,7 +757,8 @@ LInstruction* LChunkBuilder::MarkAsCall(LInstruction* instr,
   // Thus we still need to attach environment to this call even if
   // call sequence can not deoptimize eagerly.
   bool needs_environment =
-      (can_deoptimize == CAN_DEOPTIMIZE_EAGERLY) || !hinstr->HasSideEffects();
+      (can_deoptimize == CAN_DEOPTIMIZE_EAGERLY) ||
+      !hinstr->HasObservableSideEffects();
   if (needs_environment && !instr->HasEnvironment()) {
     instr = AssignEnvironment(instr);
   }

test/mjsunit/elements-kind-depends.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
+
+function burn() {
+  var a = new Array(3);
+  a[0] = 10;
+  a[1] = 15.5;
+  a[2] = 20;
+  return a;
+}
+
+function check(a) {
+  assertEquals(10, a[0]);
+  assertEquals(15.5, a[1]);
+  assertEquals(20, a[2]);
+}
+
+var b;
+for (var i = 0; i < 3; ++i) {
+  b = burn();
+  check(b);  // all OK
+}
+%OptimizeFunctionOnNextCall(burn);
+b = burn();
+check(b);  // fails
+
+
+function loop_test(x) {
+  for (i=0;i<3;i++) {
+    x[i] = (i+1) * 0.5;
+  }
+}
+
+function check2(b) {
+  assertEquals(0.5, b[0]);
+  assertEquals(1.0, b[1]);
+  assertEquals(1.5, b[2]);
+}
+
+for (var i = 0; i < 3; ++i) {
+  b = [0,1,2];
+  loop_test(b);
+  check2(b);
+}
+%OptimizeFunctionOnNextCall(loop_test);
+b = [0,1,2];
+loop_test(b);
+check2(b);