[turbofan] Reduce shl with sar/shr and same shift amount to bit-and.

src/compiler/machine-operator-reducer.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/compiler/generic-node-inl.h"
 #include "src/compiler/graph.h"
 #include "src/compiler/js-graph.h"
@@ skipping 113 matching lines @@
       }
       if (m.LeftEqualsRight()) return ReplaceInt32(0);  // x ^ x => 0
       break;
     }
     case IrOpcode::kWord32Shl: {
       Int32BinopMatcher m(node);
       if (m.right().Is(0)) return Replace(m.left().node());  // x << 0 => x
       if (m.IsFoldable()) {                                  // K << K => K
         return ReplaceInt32(m.left().Value() << m.right().Value());
       }
+      if (m.right().IsInRange(1, 31)) {
+        // (x >>> K) << K => x & ~(2^K - 1)
+        // (x >> K) << K => x & ~(2^K - 1)
+        if (m.left().IsWord32Sar() || m.left().IsWord32Shr()) {
+          Int32BinopMatcher mleft(m.left().node());
+          if (mleft.right().Is(m.right().Value())) {
+            node->set_op(machine()->Word32And());
+            node->ReplaceInput(0, mleft.left().node());
+            node->ReplaceInput(
+                1, Uint32Constant(~((1U << m.right().Value()) - 1U)));
+            return Changed(node);
+          }
+        }
+      }
       break;
     }
     case IrOpcode::kWord32Shr: {
       Uint32BinopMatcher m(node);
       if (m.right().Is(0)) return Replace(m.left().node());  // x >>> 0 => x
       if (m.IsFoldable()) {                                  // K >>> K => K
         return ReplaceInt32(m.left().Value() >> m.right().Value());
       }
       break;
     }
@@ skipping 351 matching lines @@
 MachineOperatorBuilder* MachineOperatorReducer::machine() const {
   return jsgraph()->machine();
 }
 
 
 Graph* MachineOperatorReducer::graph() const { return jsgraph()->graph(); }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8