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/*
* Copyright (C) 2007 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "clz.h"
/*
* Implementation of CLZ; intended to mimic gcc's __builtin_clz.
*
* Returns the number of leading zero bits, starting at the most
* significant bit position. If the argument is zero, the result is
* undefined.
*
* (For best results, this file should always be compiled for ARM, not THUMB.)
*/
int dvmClzImpl(unsigned int x)
{
#ifdef HAVE_BUILTIN_CLZ
/*
* This file was compiled with flags that allow it to use the built-in
* CLZ (e.g. ARM mode for ARMv5 or later).
*/
return __builtin_clz(x);
#else
/*
* Built-in version not available.
*/
if (!x) return 32;
int e = 31;
if (x&0xFFFF0000) { e -=16; x >>=16; }
if (x&0x0000FF00) { e -= 8; x >>= 8; }
if (x&0x000000F0) { e -= 4; x >>= 4; }
if (x&0x0000000C) { e -= 2; x >>= 2; }
if (x&0x00000002) { e -= 1; }
return e;
#endif
}
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