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// Copyright 2013 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#if V8_TARGET_ARCH_ARM64
#include "arm64/utils-arm64.h"
namespace v8 {
namespace internal {
#define __ assm->
int CountLeadingZeros(uint64_t value, int width) {
// TODO(jbramley): Optimize this for ARM64 hosts.
ASSERT((width == 32) || (width == 64));
int count = 0;
uint64_t bit_test = 1UL << (width - 1);
while ((count < width) && ((bit_test & value) == 0)) {
count++;
bit_test >>= 1;
}
return count;
}
int CountLeadingSignBits(int64_t value, int width) {
// TODO(jbramley): Optimize this for ARM64 hosts.
ASSERT((width == 32) || (width == 64));
if (value >= 0) {
return CountLeadingZeros(value, width) - 1;
} else {
return CountLeadingZeros(~value, width) - 1;
}
}
int CountTrailingZeros(uint64_t value, int width) {
// TODO(jbramley): Optimize this for ARM64 hosts.
ASSERT((width == 32) || (width == 64));
int count = 0;
while ((count < width) && (((value >> count) & 1) == 0)) {
count++;
}
return count;
}
int CountSetBits(uint64_t value, int width) {
// TODO(jbramley): Would it be useful to allow other widths? The
// implementation already supports them.
ASSERT((width == 32) || (width == 64));
// Mask out unused bits to ensure that they are not counted.
value &= (0xffffffffffffffffUL >> (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
value = ((value >> 1) & 0x5555555555555555) + (value & 0x5555555555555555);
value = ((value >> 2) & 0x3333333333333333) + (value & 0x3333333333333333);
value = ((value >> 4) & 0x0f0f0f0f0f0f0f0f) + (value & 0x0f0f0f0f0f0f0f0f);
value = ((value >> 8) & 0x00ff00ff00ff00ff) + (value & 0x00ff00ff00ff00ff);
value = ((value >> 16) & 0x0000ffff0000ffff) + (value & 0x0000ffff0000ffff);
value = ((value >> 32) & 0x00000000ffffffff) + (value & 0x00000000ffffffff);
return value;
}
int MaskToBit(uint64_t mask) {
ASSERT(CountSetBits(mask, 64) == 1);
return CountTrailingZeros(mask, 64);
}
} } // namespace v8::internal
#endif // V8_TARGET_ARCH_ARM64
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