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 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.

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 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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#include "precompiled.hpp"

#include "asm/assembler.hpp"

#include "asm/assembler.inline.hpp"

#include "ci/ciEnv.hpp"

#include "gc/shared/cardTableModRefBS.hpp"

#include "gc/shared/collectedHeap.inline.hpp"

#include "interpreter/interpreter.hpp"

#include "interpreter/interpreterRuntime.hpp"

#include "interpreter/templateInterpreterGenerator.hpp"

#include "memory/resourceArea.hpp"

#include "prims/jvm_misc.hpp"

#include "prims/methodHandles.hpp"

#include "runtime/biasedLocking.hpp"

#include "runtime/interfaceSupport.hpp"

#include "runtime/objectMonitor.hpp"

#include "runtime/os.hpp"

#include "runtime/sharedRuntime.hpp"

#include "runtime/stubRoutines.hpp"

#include "utilities/hashtable.hpp"

#include "utilities/macros.hpp"

#if INCLUDE_ALL_GCS

#include "gc/g1/g1CollectedHeap.inline.hpp"

#include "gc/g1/heapRegion.hpp"

#endif // INCLUDE_ALL_GCS

// Returns whether given imm has equal bit fields <0:size-1> and <size:2*size-1>.

inline bool Assembler::LogicalImmediate::has_equal_subpatterns(uintx imm, int size) {

  uintx mask = right_n_bits(size);

  uintx subpattern1 = mask_bits(imm, mask);

  uintx subpattern2 = mask_bits(imm >> size, mask);

  return subpattern1 == subpattern2;

}

// Returns least size that is a power of two from 2 to 64 with the proviso that given

// imm is composed of repeating patterns of this size.

inline int Assembler::LogicalImmediate::least_pattern_size(uintx imm) {

  int size = BitsPerWord;

  while (size > 2 && has_equal_subpatterns(imm, size >> 1)) {

    size >>= 1;

  }

  return size;

}

// Returns count of set bits in given imm. Based on variable-precision SWAR algorithm.

inline int Assembler::LogicalImmediate::population_count(uintx x) {

  x -= ((x >> 1) & 0x5555555555555555L);

  x = (((x >> 2) & 0x3333333333333333L) + (x & 0x3333333333333333L));

  x = (((x >> 4) + x) & 0x0f0f0f0f0f0f0f0fL);

  x += (x >> 8);

  x += (x >> 16);

  x += (x >> 32);

  return(x & 0x7f);

}

// Let given x be <A:B> where B = 0 and least bit of A = 1. Returns <A:C>, where C is B-size set bits.

inline uintx Assembler::LogicalImmediate::set_least_zeroes(uintx x) {

  return x | (x - 1);

}

#ifdef ASSERT

// Restores immediate by encoded bit masks.

uintx Assembler::LogicalImmediate::decode() {

  assert (_encoded, "should be");

  int len_code = (_immN << 6) | ((~_imms) & 0x3f);

  assert (len_code != 0, "should be");

  int len = 6;

  while (!is_set_nth_bit(len_code, len)) len--;

  int esize = 1 << len;

  assert (len > 0, "should be");

  assert ((_is32bit ? 32 : 64) >= esize, "should be");

  int levels = right_n_bits(len);

  int S = _imms & levels;

  int R = _immr & levels;

  assert (S != levels, "should be");

  uintx welem = right_n_bits(S + 1);

  uintx wmask = (R == 0) ? welem : ((welem >> R) | (welem << (esize - R)));

  for (int size = esize; size < 64; size <<= 1) {

    wmask |= (wmask << size);

  }

  return wmask;

}

#endif

// Constructs LogicalImmediate by given imm. Figures out if given imm can be used in AArch64 logical

// instructions (AND, ANDS, EOR, ORR) and saves its encoding.

void Assembler::LogicalImmediate::construct(uintx imm, bool is32) {

  _is32bit = is32;

  if (is32) {

    assert(((imm >> 32) == 0) || (((intx)imm >> 31) == -1), "32-bit immediate is out of range");

    // Replicate low 32 bits.

    imm &= 0xffffffff;

    imm |= imm << 32;

  }

  // All-zeroes and all-ones can not be encoded.

  if (imm != 0 && (~imm != 0)) {

    // Let LPS (least pattern size) be the least size (power of two from 2 to 64) of repeating

    // patterns in the immediate. If immediate value can be encoded, it is encoded by pattern

    // of exactly LPS size (due to structure of valid patterns). In order to verify

    // that immediate value can be encoded, LPS is calculated and <LPS-1:0> bits of immediate

    // are verified to be valid pattern.

    int lps = least_pattern_size(imm);

    uintx lps_mask = right_n_bits(lps);

    // A valid pattern has one of the following forms:

    //  | 0 x A | 1 x B | 0 x C |, where B > 0 and C > 0, or

    //  | 1 x A | 0 x B | 1 x C |, where B > 0 and C > 0.

    // For simplicity, the second form of the pattern is inverted into the first form.

    bool inverted = imm & 0x1;

    uintx pattern = (inverted ? ~imm : imm) & lps_mask;

    //  | 0 x A | 1 x (B + C)   |

    uintx without_least_zeroes = set_least_zeroes(pattern);

    // Pattern is valid iff without least zeroes it is a power of two - 1.

    if ((without_least_zeroes & (without_least_zeroes + 1)) == 0) {

      // Count B as population count of pattern.

      int bits_count = population_count(pattern);

      // Count B+C as population count of pattern without least zeroes

      int left_range = population_count(without_least_zeroes);

      // S-prefix is a part of imms field which encodes LPS.

      //  LPS  |  S prefix

      //   64  |     not defined

      //   32  |     0b0

      //   16  |     0b10

      //    8  |     0b110

      //    4  |     0b1110

      //    2  |     0b11110

      int s_prefix = (lps == 64) ? 0 : ~set_least_zeroes(lps) & 0x3f;

      // immN bit is set iff LPS == 64.

      _immN = (lps == 64) ? 1 : 0;

      assert (!is32 || (_immN == 0), "32-bit immediate should be encoded with zero N-bit");

      // immr is the rotation size.

      _immr = lps + (inverted ? 0 : bits_count) - left_range;

      // imms is the field that encodes bits count and S-prefix.

      _imms = ((inverted ? (lps - bits_count) : bits_count) - 1) | s_prefix;

      _encoded = true;

      assert (decode() == imm, "illegal encoding");

      return;

    }

  }

  _encoded = false;

}