[builtins] Migrate Math.clz32 to a TurboFan builtin.

src/compiler/simplified-lowering.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/simplified-lowering.h"
 
 #include <limits>
 
 #include "src/base/bits.h"
 #include "src/code-factory.h"
@@ skipping 944 matching lines @@
       }
       case IrOpcode::kNumberShiftRightLogical: {
         Type* rhs_type = GetUpperBound(node->InputAt(1));
         VisitBinop(node, UseInfo::TruncatingWord32(),
                    UseInfo::TruncatingWord32(), MachineRepresentation::kWord32);
         if (lower()) {
           lowering->DoShift(node, lowering->machine()->Word32Shr(), rhs_type);
         }
         break;
       }
+      case IrOpcode::kNumberClz32: {
+        VisitUnop(node, UseInfo::TruncatingWord32(),
+                  MachineRepresentation::kWord32);
+        if (lower()) NodeProperties::ChangeOp(node, Uint32Op(node));
+        break;
+      }
       case IrOpcode::kNumberCeil: {
         VisitUnop(node, UseInfo::Float64(), MachineRepresentation::kFloat64);
         if (lower()) DeferReplacement(node, lowering->Float64Ceil(node));
         break;
       }
       case IrOpcode::kNumberFloor: {
         VisitUnop(node, UseInfo::Float64(), MachineRepresentation::kFloat64);
         if (lower()) DeferReplacement(node, lowering->Float64Floor(node));
         break;
       }
@@ skipping 1209 matching lines @@
   if (!rhs_type->Is(type_cache_.kZeroToThirtyOne)) {
     node->ReplaceInput(1, graph()->NewNode(machine()->Word32And(), rhs,
                                            jsgraph()->Int32Constant(0x1f)));
   }
   NodeProperties::ChangeOp(node, op);
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8