[turbofan] Optimize Uint32LessThan with Word32Sar.

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/codegen.h"
 #include "src/compiler/generic-node-inl.h"
 #include "src/compiler/graph.h"
@@ skipping 321 matching lines @@
       break;
     }
     case IrOpcode::kUint32LessThan: {
       Uint32BinopMatcher m(node);
       if (m.left().Is(kMaxUInt32)) return ReplaceBool(false);  // M < x => false
       if (m.right().Is(0)) return ReplaceBool(false);          // x < 0 => false
       if (m.IsFoldable()) {                                    // K < K => K
         return ReplaceBool(m.left().Value() < m.right().Value());
       }
       if (m.LeftEqualsRight()) return ReplaceBool(false);  // x < x => false
+      if (m.left().IsWord32Sar() && m.right().HasValue()) {
+        Int32BinopMatcher mleft(m.left().node());
+        if (mleft.right().HasValue()) {
+          // (x >> K) < C => x < (C << K) | (2^K - 1)
+          // when C < (M >> K)
+          const uint32_t c = m.right().Value();
+          const uint32_t k = mleft.right().Value() & 0x1f;
+          if (c < static_cast<uint32_t>(kMaxInt >> k)) {
+            node->ReplaceInput(0, mleft.left().node());
+            node->ReplaceInput(1, Uint32Constant((c << k) | ((1 << k) - 1)));
+            return Changed(node);
+          }
+        }
+      }
       break;
     }
     case IrOpcode::kUint32LessThanOrEqual: {
       Uint32BinopMatcher m(node);
       if (m.left().Is(0)) return ReplaceBool(true);            // 0 <= x => true
       if (m.right().Is(kMaxUInt32)) return ReplaceBool(true);  // x <= M => true
       if (m.IsFoldable()) {                                    // K <= K => K
         return ReplaceBool(m.left().Value() <= m.right().Value());
       }
       if (m.LeftEqualsRight()) return ReplaceBool(true);  // x <= x => true
@@ skipping 189 matching lines @@
 MachineOperatorBuilder* MachineOperatorReducer::machine() const {
   return jsgraph()->machine();
 }
 
 
 Graph* MachineOperatorReducer::graph() const { return jsgraph()->graph(); }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8