Implemented the Word64Clz TurboFan operator for x64, arm64, and mips64.

src/x64/assembler-x64.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/x64/assembler-x64.h"
 
 #include <cstring>
 
 #if V8_TARGET_ARCH_X64
 
@@ skipping 727 matching lines @@
 
 void Assembler::bsrl(Register dst, const Operand& src) {
   EnsureSpace ensure_space(this);
   emit_optional_rex_32(dst, src);
   emit(0x0F);
   emit(0xBD);
   emit_operand(dst, src);
 }
 
 
+void Assembler::bsrq(Register dst, Register src) {
+  EnsureSpace ensure_space(this);
+  emit_rex_64(dst, src);
+  emit(0x0F);
+  emit(0xBD);
+  emit_modrm(dst, src);
+}
+
+
+void Assembler::bsrq(Register dst, const Operand& src) {
+  EnsureSpace ensure_space(this);
+  emit_rex_64(dst, src);
+  emit(0x0F);
+  emit(0xBD);
+  emit_operand(dst, src);
+}
+
+
 void Assembler::bsfl(Register dst, Register src) {
   EnsureSpace ensure_space(this);
   emit_optional_rex_32(dst, src);
   emit(0x0F);
   emit(0xBC);
   emit_modrm(dst, src);
 }
 
 
 void Assembler::bsfl(Register dst, const Operand& src) {
@@ skipping 3283 matching lines @@
 
 bool RelocInfo::IsInConstantPool() {
   return false;
 }
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_X64