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// Copyright 2015, ARM Limited
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
// * Redistributions of source code must retain the above copyright notice,
// this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above copyright notice,
// this list of conditions and the following disclaimer in the documentation
// and/or other materials provided with the distribution.
// * Neither the name of ARM Limited nor the names of its contributors may be
// used to endorse or promote products derived from this software without
// specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS CONTRIBUTORS "AS IS" AND
// ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
// WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE
// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
// OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#include "compiler-intrinsics.h"
namespace vixl {
int CountLeadingSignBitsFallBack(int64_t value, int width) {
VIXL_ASSERT(IsPowerOf2(width) && (width <= 64));
if (value >= 0) {
return CountLeadingZeros(value, width) - 1;
} else {
return CountLeadingZeros(~value, width) - 1;
}
}
int CountLeadingZerosFallBack(uint64_t value, int width) {
VIXL_ASSERT(IsPowerOf2(width) && (width <= 64));
if (value == 0) {
return width;
}
int count = 0;
value = value << (64 - width);
if ((value & UINT64_C(0xffffffff00000000)) == 0) {
count += 32;
value = value << 32;
}
if ((value & UINT64_C(0xffff000000000000)) == 0) {
count += 16;
value = value << 16;
}
if ((value & UINT64_C(0xff00000000000000)) == 0) {
count += 8;
value = value << 8;
}
if ((value & UINT64_C(0xf000000000000000)) == 0) {
count += 4;
value = value << 4;
}
if ((value & UINT64_C(0xc000000000000000)) == 0) {
count += 2;
value = value << 2;
}
if ((value & UINT64_C(0x8000000000000000)) == 0) {
count += 1;
}
count += (value == 0);
return count;
}
int CountSetBitsFallBack(uint64_t value, int width) {
VIXL_ASSERT(IsPowerOf2(width) && (width <= 64));
// Mask out unused bits to ensure that they are not counted.
value &= (UINT64_C(0xffffffffffffffff) >> (64 - width));
// Add up the set bits.
// The algorithm works by adding pairs of bit fields together iteratively,
// where the size of each bit field doubles each time.
// An example for an 8-bit value:
// Bits: h g f e d c b a
// \ | \ | \ | \ |
// value = h+g f+e d+c b+a
// \ | \ |
// value = h+g+f+e d+c+b+a
// \ |
// value = h+g+f+e+d+c+b+a
const uint64_t kMasks[] = {
UINT64_C(0x5555555555555555),
UINT64_C(0x3333333333333333),
UINT64_C(0x0f0f0f0f0f0f0f0f),
UINT64_C(0x00ff00ff00ff00ff),
UINT64_C(0x0000ffff0000ffff),
UINT64_C(0x00000000ffffffff),
};
for (unsigned i = 0; i < (sizeof(kMasks) / sizeof(kMasks[0])); i++) {
int shift = 1 << i;
value = ((value >> shift) & kMasks[i]) + (value & kMasks[i]);
}
return static_cast<int>(value);
}
int CountTrailingZerosFallBack(uint64_t value, int width) {
VIXL_ASSERT(IsPowerOf2(width) && (width <= 64));
int count = 0;
value = value << (64 - width);
if ((value & UINT64_C(0xffffffff)) == 0) {
count += 32;
value = value >> 32;
}
if ((value & 0xffff) == 0) {
count += 16;
value = value >> 16;
}
if ((value & 0xff) == 0) {
count += 8;
value = value >> 8;
}
if ((value & 0xf) == 0) {
count += 4;
value = value >> 4;
}
if ((value & 0x3) == 0) {
count += 2;
value = value >> 2;
}
if ((value & 0x1) == 0) {
count += 1;
}
count += (value == 0);
return count - (64 - width);
}
} // namespace vixl
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