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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