X87: [turbofan] Turn Math.clz32 into an inlinable builtin.

src/x87/lithium-codegen-x87.cc

 // Copyright 2012 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/v8.h"
 
 #if V8_TARGET_ARCH_X87
 
 #include "src/base/bits.h"
 #include "src/code-factory.h"
@@ skipping 4276 matching lines @@
   __ fld_d(Operand::StaticVariable(ninf));
   X87CommitWrite(input_reg);
 
   __ bind(&done);
 }
 
 
 void LCodeGen::DoMathClz32(LMathClz32* instr) {
   Register input = ToRegister(instr->value());
   Register result = ToRegister(instr->result());
-  Label not_zero_input;
-  __ bsr(result, input);
 
-  __ j(not_zero, &not_zero_input);
-  __ Move(result, Immediate(63));  // 63^31 == 32
-
-  __ bind(&not_zero_input);
-  __ xor_(result, Immediate(31));  // for x in [0..31], 31^x == 31-x.
+  __ Lzcnt(result, input);
 }
 
 
 void LCodeGen::DoMathExp(LMathExp* instr) {
   X87Register input = ToX87Register(instr->value());
   X87Register result_reg = ToX87Register(instr->result());
   Register temp_result = ToRegister(instr->temp1());
   Register temp = ToRegister(instr->temp2());
   Label slow, done, smi, finish;
   DCHECK(result_reg.is(input));
@@ skipping 2098 matching lines @@
   CallRuntime(Runtime::kPushBlockContext, 2, instr);
   RecordSafepoint(Safepoint::kNoLazyDeopt);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X87