1 /* 2 * Copyright (c) 2017, 2019, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #ifndef SHARE_UTILITIES_COUNT_TRAILING_ZEROS_HPP 26 #define SHARE_UTILITIES_COUNT_TRAILING_ZEROS_HPP 27 28 #include "utilities/debug.hpp" 29 #include "utilities/globalDefinitions.hpp" 30 31 // unsigned count_trailing_zeros(uintx x) 32 // Return the number of trailing zeros in x, e.g. the zero-based index 33 // of the least significant set bit in x. 34 // Precondition: x != 0. 35 36 // Dispatch on toolchain to select implementation. 37 38 /***************************************************************************** 39 * GCC and compatible (including Clang) 40 *****************************************************************************/ 41 #if defined(TARGET_COMPILER_gcc) 42 43 inline unsigned count_trailing_zeros(uintx x) { 44 STATIC_ASSERT(sizeof(unsigned long) == sizeof(uintx)); 45 assert(x != 0, "precondition"); 46 return __builtin_ctzl(x); 47 } 48 49 /***************************************************************************** 50 * Microsoft Visual Studio 51 *****************************************************************************/ 52 #elif defined(TARGET_COMPILER_visCPP) 53 54 #include <intrin.h> 55 56 #ifdef _LP64 57 #pragma intrinsic(_BitScanForward64) 58 #else 59 #pragma intrinsic(_BitScanForward) 60 #endif 61 62 inline unsigned count_trailing_zeros(uintx x) { 63 assert(x != 0, "precondition"); 64 unsigned long index; 65 #ifdef _LP64 66 _BitScanForward64(&index, x); 67 #else 68 _BitScanForward(&index, x); 69 #endif 70 return index; 71 } 72 73 /***************************************************************************** 74 * IBM XL C/C++ 75 *****************************************************************************/ 76 #elif defined(TARGET_COMPILER_xlc) 77 78 #include <builtins.h> 79 80 inline unsigned count_trailing_zeros(uintx x) { 81 assert(x != 0, "precondition"); 82 #ifdef _LP64 83 return __cnttz8(x); 84 #else 85 return __cnttz4(x); 86 #endif 87 } 88 89 /***************************************************************************** 90 * Oracle Studio 91 *****************************************************************************/ 92 #elif defined(TARGET_COMPILER_solstudio) 93 94 // No compiler built-in / intrinsic, so use inline assembler. 95 96 #include "utilities/macros.hpp" 97 98 #include OS_CPU_HEADER(count_trailing_zeros) 99 100 /***************************************************************************** 101 * Unknown toolchain 102 *****************************************************************************/ 103 #else 104 #error Unknown TARGET_COMPILER 105 106 #endif // Toolchain dispatch 107 108 #endif // SHARE_UTILITIES_COUNT_TRAILING_ZEROS_HPP