[turbofan] Replace shr of masked bits with zero

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

 // 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.
 
 #include "src/compiler/machine-operator-reducer.h"
 #include "src/base/bits.h"
 #include "src/base/division-by-constant.h"
 #include "src/base/ieee754.h"
 #include "src/compiler/js-graph.h"
 #include "src/compiler/typer.h"
@@ skipping 832 matching lines @@
         machine()->Word32Sar(),
         graph()->NewNode(machine()->Word32Shl(), l, Int32Constant(16)),
         Int32Constant(16)));
     ASSERT_TRUE(r.Changed());
     EXPECT_EQ(l, r.replacement());
   }
 }
 
 
 // -----------------------------------------------------------------------------
+// Word32Shr
+
+TEST_F(MachineOperatorReducerTest, Word32ShrWithWord32And) {
+  Node* const p0 = Parameter(0);
+  TRACED_FORRANGE(int32_t, shift, 1, 31) {
+    uint32_t mask = (1 << shift) - 1;
+    Node* node = graph()->NewNode(
+        machine()->Word32Shr(),
+        graph()->NewNode(machine()->Word32And(), p0, Int32Constant(mask)),
+        Int32Constant(shift));
+    Reduction r = Reduce(node);
+    ASSERT_TRUE(r.Changed());
+    EXPECT_THAT(r.replacement(), IsInt32Constant(0));
+  }
+}
+
+// -----------------------------------------------------------------------------
 // Word32Shl
 
-
 TEST_F(MachineOperatorReducerTest, Word32ShlWithZeroShift) {
   Node* p0 = Parameter(0);
   Node* node = graph()->NewNode(machine()->Word32Shl(), p0, Int32Constant(0));
   Reduction r = Reduce(node);
   ASSERT_TRUE(r.Changed());
   EXPECT_EQ(p0, r.replacement());
 }
 
 
 TEST_F(MachineOperatorReducerTest, Word32ShlWithWord32Sar) {
@@ skipping 852 matching lines @@
     Reduction r = Reduce(node);
     ASSERT_TRUE(r.Changed());
     EXPECT_THAT(r.replacement(),
                 IsStore(rep, base, index, value, effect, control));
   }
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8