Synchronize with r15701.

src/hydrogen-minus-zero.cc

Index: src/hydrogen-minus-zero.cc
diff --git a/src/hydrogen-redundant-phi.cc b/src/hydrogen-minus-zero.cc
similarity index 50%
copy from src/hydrogen-redundant-phi.cc
copy to src/hydrogen-minus-zero.cc
index 9c38200577d4994e79f5e1925039ca10a8c8a8c2..e9628959deeec1b9d3159f397bdd1a9ba9fc49a0 100644
--- a/src/hydrogen-redundant-phi.cc
+++ b/src/hydrogen-minus-zero.cc
@@ -25,52 +25,59 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-#include "hydrogen-redundant-phi.h"
+#include "hydrogen-minus-zero.h"
 
 namespace v8 {
 namespace internal {
 
-void HRedundantPhiEliminationPhase::Run() {
-  // We do a simple fixed point iteration without any work list, because
-  // machine-generated JavaScript can lead to a very dense Hydrogen graph with
-  // an enormous work list and will consequently result in OOM. Experiments
-  // showed that this simple algorithm is good enough, and even e.g. tracking
-  // the set or range of blocks to consider is not a real improvement.
-  bool need_another_iteration;
+void HComputeMinusZeroChecksPhase::Run() {
   const ZoneList<HBasicBlock*>* blocks(graph()->blocks());
-  ZoneList<HPhi*> redundant_phis(blocks->length(), zone());
-  do {
-    need_another_iteration = false;
-    for (int i = 0; i < blocks->length(); ++i) {
-      HBasicBlock* block = blocks->at(i);
-      for (int j = 0; j < block->phis()->length(); j++) {
-        HPhi* phi = block->phis()->at(j);
-        HValue* replacement = phi->GetRedundantReplacement();
-        if (replacement != NULL) {
-          // Remember phi to avoid concurrent modification of the block's phis.
-          redundant_phis.Add(phi, zone());
-          for (HUseIterator it(phi->uses()); !it.Done(); it.Advance()) {
-            HValue* value = it.value();
-            value->SetOperandAt(it.index(), replacement);
-            need_another_iteration |= value->IsPhi();
-          }
+  for (int i = 0; i < blocks->length(); ++i) {
+    for (HInstructionIterator it(blocks->at(i)); !it.Done(); it.Advance()) {
+      HInstruction* current = it.Current();
+      if (current->IsChange()) {
+        HChange* change = HChange::cast(current);
+        // Propagate flags for negative zero checks upwards from conversions
+        // int32-to-tagged and int32-to-double.
+        Representation from = change->value()->representation();
+        ASSERT(from.Equals(change->from()));
+        if (from.IsInteger32()) {
+          ASSERT(change->to().IsTagged() ||
+                 change->to().IsDouble() ||
+                 change->to().IsSmi());
+          ASSERT(visited_.IsEmpty());
+          PropagateMinusZeroChecks(change->value());
+          visited_.Clear();
         }
       }
-      for (int i = 0; i < redundant_phis.length(); i++) {
-        block->RemovePhi(redundant_phis[i]);
+    }
+  }
+}
+
+
+void HComputeMinusZeroChecksPhase::PropagateMinusZeroChecks(HValue* value) {
+  for (HValue* current = value;
+       current != NULL && !visited_.Contains(current->id());
+       current = current->EnsureAndPropagateNotMinusZero(&visited_)) {
+    // For phis, we must propagate the check to all of its inputs.
+    if (current->IsPhi()) {
+      visited_.Add(current->id());
+      HPhi* phi = HPhi::cast(current);
+      for (int i = 0; i < phi->OperandCount(); ++i) {
+        PropagateMinusZeroChecks(phi->OperandAt(i));
       }
-      redundant_phis.Clear();
+      break;
     }
-  } while (need_another_iteration);
 
-#if DEBUG
-  // Make sure that we *really* removed all redundant phis.
-  for (int i = 0; i < blocks->length(); ++i) {
-    for (int j = 0; j < blocks->at(i)->phis()->length(); j++) {
-      ASSERT(blocks->at(i)->phis()->at(j)->GetRedundantReplacement() == NULL);
+    // For multiplication, division, and Math.min/max(), we must propagate
+    // to the left and the right side.
+    if (current->IsMul() || current->IsDiv() || current->IsMathMinMax()) {
+      HBinaryOperation* operation = HBinaryOperation::cast(current);
+      operation->EnsureAndPropagateNotMinusZero(&visited_);
+      PropagateMinusZeroChecks(operation->left());
+      PropagateMinusZeroChecks(operation->right());
     }
   }
-#endif
 }
 
 } }  // namespace v8::internal