src/hotspot/share/utilities/count_trailing_zeros.hpp
author ihse
Fri, 31 Aug 2018 09:37:03 +0200
changeset 51605 2ca553d34949
parent 47216 71c04702a3d5
child 53244 9807daeb47c4
permissions -rw-r--r--
6657100: Rename sparcWorks to solstudio in HotSpot Reviewed-by: erikj, dcubed
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/*
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 * Copyright (c) 2017, Oracle and/or its affiliates. All rights reserved.
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 *
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 * This code is free software; you can redistribute it and/or modify it
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 * under the terms of the GNU General Public License version 2 only, as
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 * published by the Free Software Foundation.
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 *
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 * This code is distributed in the hope that it will be useful, but WITHOUT
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 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
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 * version 2 for more details (a copy is included in the LICENSE file that
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 * accompanied this code).
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 *
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 * You should have received a copy of the GNU General Public License version
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 * 2 along with this work; if not, write to the Free Software Foundation,
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 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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 *
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 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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 * or visit www.oracle.com if you need additional information or have any
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 * questions.
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 *
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 */
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#ifndef SHARE_VM_UTILITIES_COUNTTRAILINGZEROS_HPP
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#define SHARE_VM_UTILITIES_COUNTTRAILINGZEROS_HPP
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#include "utilities/debug.hpp"
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#include "utilities/globalDefinitions.hpp"
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// unsigned count_trailing_zeros(uintx x)
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// Return the number of trailing zeros in x, e.g. the zero-based index
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// of the least significant set bit in x.
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// Precondition: x != 0.
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// Dispatch on toolchain to select implementation.
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/*****************************************************************************
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 * GCC and compatible (including Clang)
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 *****************************************************************************/
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#if defined(TARGET_COMPILER_gcc)
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inline unsigned count_trailing_zeros(uintx x) {
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  STATIC_ASSERT(sizeof(unsigned long) == sizeof(uintx));
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  assert(x != 0, "precondition");
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  return __builtin_ctzl(x);
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}
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/*****************************************************************************
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 * Microsoft Visual Studio
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 *****************************************************************************/
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#elif defined(TARGET_COMPILER_visCPP)
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#include <intrin.h>
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#ifdef _LP64
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#pragma intrinsic(_BitScanForward64)
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#else
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#pragma intrinsic(_BitScanForward)
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#endif
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inline unsigned count_trailing_zeros(uintx x) {
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  assert(x != 0, "precondition");
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  unsigned long index;
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#ifdef _LP64
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  _BitScanForward64(&index, x);
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#else
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  _BitScanForward(&index, x);
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#endif
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  return index;
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}
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/*****************************************************************************
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 * IBM XL C/C++
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 *****************************************************************************/
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#elif defined(TARGET_COMPILER_xlc)
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#include <builtins.h>
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inline unsigned count_trailing_zeros(uintx x) {
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  assert(x != 0, "precondition");
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#ifdef _LP64
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  return __cnttz8(x);
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#else
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  return __cnttz4(x);
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#endif
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}
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/*****************************************************************************
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 * Oracle Studio
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 *****************************************************************************/
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#elif defined(TARGET_COMPILER_solstudio)
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// No compiler built-in / intrinsic, so use inline assembler.
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#include "utilities/macros.hpp"
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#include OS_CPU_HEADER(count_trailing_zeros)
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/*****************************************************************************
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 * Unknown toolchain
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 *****************************************************************************/
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#else
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#error Unknown TARGET_COMPILER
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#endif // Toolchain dispatch
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#endif // include guard