1 /* 2 * Copyright (C) 2007 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 /* 18 * Implementation of clz(), which returns the number of leading zero bits, 19 * starting at the most significant bit position. If the argument is zero, 20 * the result is undefined. 21 * 22 * On some platforms, gcc provides a __builtin_clz() function that uses 23 * an optimized implementation (e.g. the CLZ instruction on ARM). 24 * 25 * This gets a little tricky for ARM, because it's only available in ARMv5 26 * and above, and even on ARMv5 it's not available for THUMB code. So we 27 * need to tailor this for every source file. 28 */ 29 #ifndef _DALVIK_CLZ 30 31 #if defined(__arm__) && !defined(__thumb__) 32 # include <machine/cpu-features.h> 33 # if defined(__ARM_HAVE_CLZ) 34 # define CLZ(x) __builtin_clz(x) 35 # define HAVE_BUILTIN_CLZ 36 # endif 37 #endif 38 39 #ifndef HAVE_BUILTIN_CLZ 40 # define CLZ(x) dvmClzImpl(x) 41 int dvmClzImpl(unsigned int x); 42 #endif 43 44 #endif // _DALVIK_CLZ 45
