[turbofan] Reduce (x & K) & K to x & K.

TEST=unittests
R=dcarney@chromium.org

Review URL: https://codereview.chromium.org/685713002

Cr-Commit-Position: refs/heads/master@{#24931}
git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24931 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/compiler/machine-operator-reducer.cc

@@ -109,6 +109,15 @@ Reduction MachineOperatorReducer::Reduce(Node* node) {
         return ReplaceInt32(m.left().Value() & m.right().Value());
       }
       if (m.LeftEqualsRight()) return Replace(m.left().node());  // x & x => x
+      if (m.left().IsWord32And() && m.right().HasValue()) {
+        Int32BinopMatcher mleft(m.left().node());
+        if (mleft.right().HasValue()) {  // (x & K) & K => x & K
+          node->ReplaceInput(0, mleft.left().node());
+          node->ReplaceInput(
+              1, Int32Constant(m.right().Value() & mleft.right().Value()));
+          return Changed(node);
+        }
+      }
       break;
     }
     case IrOpcode::kWord32Or: {

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

@@ -481,6 +481,37 @@ TEST_F(MachineOperatorReducerTest, TruncateInt64ToInt32WithConstant) {
 }
 
 
+// -----------------------------------------------------------------------------
+// Word32And
+
+
+TEST_F(MachineOperatorReducerTest, Word32AndWithWord32AndWithConstant) {
+  Node* const p0 = Parameter(0);
+
+  TRACED_FOREACH(int32_t, k, kInt32Values) {
+    TRACED_FOREACH(int32_t, l, kInt32Values) {
+      if (k == 0 || k == -1 || l == 0 || l == -1) continue;
+
+      // (x & K) & L => x & (K & L)
+      Reduction const r1 = Reduce(graph()->NewNode(
+          machine()->Word32And(),
+          graph()->NewNode(machine()->Word32And(), p0, Int32Constant(k)),
+          Int32Constant(l)));
+      ASSERT_TRUE(r1.Changed());
+      EXPECT_THAT(r1.replacement(), IsWord32And(p0, IsInt32Constant(k & l)));
+
+      // (K & x) & L => x & (K & L)
+      Reduction const r2 = Reduce(graph()->NewNode(
+          machine()->Word32And(),
+          graph()->NewNode(machine()->Word32And(), Int32Constant(k), p0),
+          Int32Constant(l)));
+      ASSERT_TRUE(r2.Changed());
+      EXPECT_THAT(r2.replacement(), IsWord32And(p0, IsInt32Constant(k & l)));
+    }
+  }
+}
+
+
 // -----------------------------------------------------------------------------
 // Word32Xor