disas: Add subset of libvixl sources for A64 disassembler

Add the subset of the libvixl sources that are needed for the
A64 disassembler support. These sources come from
https://github.com/armvixl/vixl commit 578645f14e122d2b
which is VIXL release 1.1.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <rth@twiddle.net>

1 files changed, 120 insertions, 0 deletions

diff --git a/disas/libvixl/utils.cc b/disas/libvixl/utils.cc
new file mode 100644
index 0000000000..6f85e61835
--- /dev/null
+++ b/disas/libvixl/utils.cc
@@ -0,0 +1,120 @@
+// Copyright 2013, 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 "utils.h"
+#include <stdio.h>
+
+namespace vixl {
+
+uint32_t float_to_rawbits(float value) {
+  uint32_t bits = 0;
+  memcpy(&bits, &value, 4);
+  return bits;
+}
+
+
+uint64_t double_to_rawbits(double value) {
+  uint64_t bits = 0;
+  memcpy(&bits, &value, 8);
+  return bits;
+}
+
+
+float rawbits_to_float(uint32_t bits) {
+  float value = 0.0;
+  memcpy(&value, &bits, 4);
+  return value;
+}
+
+
+double rawbits_to_double(uint64_t bits) {
+  double value = 0.0;
+  memcpy(&value, &bits, 8);
+  return value;
+}
+
+
+int CountLeadingZeros(uint64_t value, int width) {
+  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) {
+  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) {
+  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: Other widths could be added here, as 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;
+}
+}  // namespace vixl