[turbofan] Push TruncateFloat64ToInt32 into phis.

TEST=unittests
R=dcarney@chromium.org

Review URL: https://codereview.chromium.org/707683003

Cr-Commit-Position: refs/heads/master@{#25189}
git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@25189 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/compiler/machine-operator-reducer.cc

@@ -523,12 +523,8 @@ Reduction MachineOperatorReducer::Reduce(Node* node) {
       if (m.HasValue()) return ReplaceInt64(static_cast<uint64_t>(m.Value()));
       break;
     }
-    case IrOpcode::kTruncateFloat64ToInt32: {
-      Float64Matcher m(node->InputAt(0));
-      if (m.HasValue()) return ReplaceInt32(DoubleToInt32(m.Value()));
-      if (m.IsChangeInt32ToFloat64()) return Replace(m.node()->InputAt(0));
-      break;
-    }
+    case IrOpcode::kTruncateFloat64ToInt32:
+      return ReduceTruncateFloat64ToInt32(node);
     case IrOpcode::kTruncateInt64ToInt32: {
       Int64Matcher m(node->InputAt(0));
       if (m.HasValue()) return ReplaceInt32(static_cast<int32_t>(m.Value()));
@@ -692,6 +688,36 @@ Reduction MachineOperatorReducer::ReduceUint32Mod(Node* node) {
 }
 
 
+Reduction MachineOperatorReducer::ReduceTruncateFloat64ToInt32(Node* node) {
+  Float64Matcher m(node->InputAt(0));
+  if (m.HasValue()) return ReplaceInt32(DoubleToInt32(m.Value()));
+  if (m.IsChangeInt32ToFloat64()) return Replace(m.node()->InputAt(0));
+  if (m.IsPhi()) {
+    Node* const phi = m.node();
+    DCHECK_EQ(kRepFloat64, RepresentationOf(OpParameter<MachineType>(phi)));
+    if (phi->OwnedBy(node)) {
+      // TruncateFloat64ToInt32(Phi[Float64](x1,...,xn))
+      //   => Phi[Int32](TruncateFloat64ToInt32(x1),
+      //                 ...,
+      //                 TruncateFloat64ToInt32(xn))
+      const int value_input_count = phi->InputCount() - 1;
+      for (int i = 0; i < value_input_count; ++i) {
+        Node* input = graph()->NewNode(machine()->TruncateFloat64ToInt32(),
+                                       phi->InputAt(i));
+        // TODO(bmeurer): Reschedule input for reduction once we have Revisit()
+        // instead of recursing into ReduceTruncateFloat64ToInt32() here.
+        Reduction reduction = ReduceTruncateFloat64ToInt32(input);
+        if (reduction.Changed()) input = reduction.replacement();
+        phi->ReplaceInput(i, input);
+      }
+      phi->set_op(common()->Phi(kMachInt32, value_input_count));
+      return Replace(phi);
+    }
+  }
+  return NoChange();
+}
+
+
 Reduction MachineOperatorReducer::ReduceStore(Node* node) {
   MachineType const rep =
       RepresentationOf(StoreRepresentationOf(node->op()).machine_type());

src/compiler/machine-operator-reducer.h

@@ -65,6 +65,7 @@ class MachineOperatorReducer FINAL : public Reducer {
   Reduction ReduceUint32Div(Node* node);
   Reduction ReduceInt32Mod(Node* node);
   Reduction ReduceUint32Mod(Node* node);
+  Reduction ReduceTruncateFloat64ToInt32(Node* node);
   Reduction ReduceStore(Node* node);
   Reduction ReduceProjection(size_t index, Node* node);
 

test/unittests/compiler/machine-operator-reducer-unittest.cc

@@ -455,6 +455,20 @@ TEST_F(MachineOperatorReducerTest, TruncateFloat64ToInt32WithConstant) {
 }
 
 
+TEST_F(MachineOperatorReducerTest, TruncateFloat64ToInt32WithPhi) {
+  Node* const p0 = Parameter(0);
+  Node* const p1 = Parameter(1);
+  Node* const merge = graph()->start();
+  Reduction reduction = Reduce(graph()->NewNode(
+      machine()->TruncateFloat64ToInt32(),
+      graph()->NewNode(common()->Phi(kMachFloat64, 2), p0, p1, merge)));
+  ASSERT_TRUE(reduction.Changed());
+  EXPECT_THAT(reduction.replacement(),
+              IsPhi(kMachInt32, IsTruncateFloat64ToInt32(p0),
+                    IsTruncateFloat64ToInt32(p1), merge));
+}
+
+
 // -----------------------------------------------------------------------------
 // TruncateInt64ToInt32