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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

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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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#ifndef OS_CPU_LINUX_S390_ATOMIC_LINUX_S390_HPP

#define OS_CPU_LINUX_S390_ATOMIC_LINUX_S390_HPP

#include "runtime/atomic.hpp"

#include "runtime/os.hpp"

#include "vm_version_s390.hpp"

// Note that the compare-and-swap instructions on System z perform

// a serialization function before the storage operand is fetched

// and again after the operation is completed.

//

// Used constraint modifiers:

// = write-only access: Value on entry to inline-assembler code irrelevant.

// + read/write access: Value on entry is used; on exit value is changed.

//   read-only  access: Value on entry is used and never changed.

// & early-clobber access: Might be modified before all read-only operands

//                         have been used.

// a address register operand (not GR0).

// d general register operand (including GR0)

// Q memory operand w/o index register.

// 0..9 operand reference (by operand position).

//      Used for operands that fill multiple roles. One example would be a

//      write-only operand receiving its initial value from a read-only operand.

//      Refer to cmpxchg(..) operand #0 and variable cmp_val for a real-life example.

//

// On System z, all store operations are atomic if the address where the data is stored into

// is an integer multiple of the data length. Furthermore, all stores are ordered:

// a store which occurs conceptually before another store becomes visible to other CPUs

// before the other store becomes visible.

//------------

// Atomic::add

//------------

// These methods force the value in memory to be augmented by the passed increment.

// Both, memory value and increment, are treated as 32bit signed binary integers.

// No overflow exceptions are recognized, and the condition code does not hold

// information about the value in memory.

//

// The value in memory is updated by using a compare-and-swap instruction. The

// instruction is retried as often as required.

//

// The return value of the method is the value that was successfully stored. At the

// time the caller receives back control, the value in memory may have changed already.

// New atomic operations only include specific-operand-serialization, not full

// memory barriers. We can use the Fast-BCR-Serialization Facility for them.

inline void z196_fast_sync() {

  __asm__ __volatile__ ("bcr 14, 0" : : : "memory");

}

template<size_t byte_size>

struct Atomic::PlatformAdd

  : Atomic::AddAndFetch<Atomic::PlatformAdd<byte_size> >

{

  template<typename I, typename D>

  D add_and_fetch(I add_value, D volatile* dest, atomic_memory_order order) const;

};

template<>

template<typename I, typename D>

inline D Atomic::PlatformAdd<4>::add_and_fetch(I inc, D volatile* dest,

                                               atomic_memory_order order) const {

  STATIC_ASSERT(4 == sizeof(I));

  STATIC_ASSERT(4 == sizeof(D));

  D old, upd;

  if (VM_Version::has_LoadAndALUAtomicV1()) {

    if (order == memory_order_conservative) { z196_fast_sync(); }

    __asm__ __volatile__ (

      "   LGFR     0,%[inc]                \n\t" // save increment

      "   LA       3,%[mem]                \n\t" // force data address into ARG2

//    "   LAA      %[upd],%[inc],%[mem]    \n\t" // increment and get old value

//    "   LAA      2,0,0(3)                \n\t" // actually coded instruction

      "   .byte    0xeb                    \n\t" // LAA main opcode

      "   .byte    0x20                    \n\t" // R1,R3

      "   .byte    0x30                    \n\t" // R2,disp1

      "   .byte    0x00                    \n\t" // disp2,disp3

      "   .byte    0x00                    \n\t" // disp4,disp5

      "   .byte    0xf8                    \n\t" // LAA minor opcode

      "   AR       2,0                     \n\t" // calc new value in register

      "   LR       %[upd],2                \n\t" // move to result register

      //---<  outputs  >---

      : [upd]  "=&d" (upd)    // write-only, updated counter value

      , [mem]  "+Q"  (*dest)  // read/write, memory to be updated atomically

      //---<  inputs  >---

      : [inc]  "a"   (inc)    // read-only.

      //---<  clobbered  >---

      : "cc", "r0", "r2", "r3", "memory"

    );

    if (order == memory_order_conservative) { z196_fast_sync(); }

  } else {

    __asm__ __volatile__ (

      "   LLGF     %[old],%[mem]           \n\t" // get old value

      "0: LA       %[upd],0(%[inc],%[old]) \n\t" // calc result

      "   CS       %[old],%[upd],%[mem]    \n\t" // try to xchg res with mem

      "   JNE      0b                      \n\t" // no success? -> retry

      //---<  outputs  >---

      : [old] "=&a" (old)    // write-only, old counter value

      , [upd] "=&d" (upd)    // write-only, updated counter value

      , [mem] "+Q"  (*dest)  // read/write, memory to be updated atomically

      //---<  inputs  >---

      : [inc] "a"   (inc)    // read-only.

      //---<  clobbered  >---

      : "cc", "memory"

    );

  }

  return upd;

}

template<>

template<typename I, typename D>

inline D Atomic::PlatformAdd<8>::add_and_fetch(I inc, D volatile* dest,

                                               atomic_memory_order order) const {

  STATIC_ASSERT(8 == sizeof(I));

  STATIC_ASSERT(8 == sizeof(D));

  D old, upd;

  if (VM_Version::has_LoadAndALUAtomicV1()) {

    if (order == memory_order_conservative) { z196_fast_sync(); }

    __asm__ __volatile__ (

      "   LGR      0,%[inc]                \n\t" // save increment

      "   LA       3,%[mem]                \n\t" // force data address into ARG2

//    "   LAAG     %[upd],%[inc],%[mem]    \n\t" // increment and get old value

//    "   LAAG     2,0,0(3)                \n\t" // actually coded instruction

      "   .byte    0xeb                    \n\t" // LAA main opcode

      "   .byte    0x20                    \n\t" // R1,R3

      "   .byte    0x30                    \n\t" // R2,disp1

      "   .byte    0x00                    \n\t" // disp2,disp3

      "   .byte    0x00                    \n\t" // disp4,disp5

      "   .byte    0xe8                    \n\t" // LAA minor opcode

      "   AGR      2,0                     \n\t" // calc new value in register

      "   LGR      %[upd],2                \n\t" // move to result register

      //---<  outputs  >---

      : [upd]  "=&d" (upd)    // write-only, updated counter value

      , [mem]  "+Q"  (*dest)  // read/write, memory to be updated atomically

      //---<  inputs  >---

      : [inc]  "a"   (inc)    // read-only.

      //---<  clobbered  >---

      : "cc", "r0", "r2", "r3", "memory"

    );

    if (order == memory_order_conservative) { z196_fast_sync(); }

  } else {

    __asm__ __volatile__ (

      "   LG       %[old],%[mem]           \n\t" // get old value

      "0: LA       %[upd],0(%[inc],%[old]) \n\t" // calc result

      "   CSG      %[old],%[upd],%[mem]    \n\t" // try to xchg res with mem

      "   JNE      0b                      \n\t" // no success? -> retry

      //---<  outputs  >---

      : [old] "=&a" (old)    // write-only, old counter value

      , [upd] "=&d" (upd)    // write-only, updated counter value

      , [mem] "+Q"  (*dest)  // read/write, memory to be updated atomically

      //---<  inputs  >---

      : [inc] "a"   (inc)    // read-only.

      //---<  clobbered  >---

      : "cc", "memory"

    );

  }

  return upd;

}

//-------------

// Atomic::xchg

//-------------

// These methods force the value in memory to be replaced by the new value passed

// in as argument.

//

// The value in memory is replaced by using a compare-and-swap instruction. The

// instruction is retried as often as required. This makes sure that the new

// value can be seen, at least for a very short period of time, by other CPUs.

//

// If we would use a normal "load(old value) store(new value)" sequence,

// the new value could be lost unnoticed, due to a store(new value) from

// another thread.

//

// The return value is the (unchanged) value from memory as it was when the

// replacement succeeded.

template<>

template<typename T>

inline T Atomic::PlatformXchg<4>::operator()(T exchange_value,

                                             T volatile* dest,

                                             atomic_memory_order unused) const {

  STATIC_ASSERT(4 == sizeof(T));

  T old;

  __asm__ __volatile__ (

    "   LLGF     %[old],%[mem]           \n\t" // get old value

    "0: CS       %[old],%[upd],%[mem]    \n\t" // try to xchg upd with mem

    "   JNE      0b                      \n\t" // no success? -> retry

    //---<  outputs  >---

    : [old] "=&d" (old)      // write-only, prev value irrelevant

    , [mem] "+Q"  (*dest)    // read/write, memory to be updated atomically

    //---<  inputs  >---

    : [upd] "d"   (exchange_value) // read-only, value to be written to memory

    //---<  clobbered  >---

    : "cc", "memory"

  );

  return old;

}

template<>

template<typename T>

inline T Atomic::PlatformXchg<8>::operator()(T exchange_value,

                                             T volatile* dest,

                                             atomic_memory_order unused) const {

  STATIC_ASSERT(8 == sizeof(T));

  T old;

  __asm__ __volatile__ (

    "   LG       %[old],%[mem]           \n\t" // get old value

    "0: CSG      %[old],%[upd],%[mem]    \n\t" // try to xchg upd with mem

    "   JNE      0b                      \n\t" // no success? -> retry

    //---<  outputs  >---

    : [old] "=&d" (old)      // write-only, init from memory

    , [mem] "+Q"  (*dest)    // read/write, memory to be updated atomically

    //---<  inputs  >---

    : [upd] "d"   (exchange_value) // read-only, value to be written to memory

    //---<  clobbered  >---

    : "cc", "memory"

  );

  return old;

}

//----------------

// Atomic::cmpxchg

//----------------

// These methods compare the value in memory with a given compare value.

// If both values compare equal, the value in memory is replaced with

// the exchange value.

//

// The value in memory is compared and replaced by using a compare-and-swap

// instruction. The instruction is NOT retried (one shot only).

//

// The return value is the (unchanged) value from memory as it was when the

// compare-and-swap instruction completed. A successful exchange operation

// is indicated by (return value == compare_value). If unsuccessful, a new

// exchange value can be calculated based on the return value which is the

// latest contents of the memory location.

//

// Inspecting the return value is the only way for the caller to determine

// if the compare-and-swap instruction was successful:

// - If return value and compare value compare equal, the compare-and-swap

//   instruction was successful and the value in memory was replaced by the

//   exchange value.

// - If return value and compare value compare unequal, the compare-and-swap

//   instruction was not successful. The value in memory was left unchanged.

//

// The s390 processors always fence before and after the csg instructions.

// Thus we ignore the memory ordering argument. The docu says: "A serialization

// function is performed before the operand is fetched and again after the

// operation is completed."

// No direct support for cmpxchg of bytes; emulate using int.

template<>

struct Atomic::PlatformCmpxchg<1> : Atomic::CmpxchgByteUsingInt {};

template<>

template<typename T>

inline T Atomic::PlatformCmpxchg<4>::operator()(T xchg_val,

                                                T volatile* dest,

                                                T cmp_val,

                                                atomic_memory_order unused) const {

  STATIC_ASSERT(4 == sizeof(T));

  T old;

  __asm__ __volatile__ (

    "   CS       %[old],%[upd],%[mem]    \n\t" // Try to xchg upd with mem.

    // outputs

    : [old] "=&d" (old)      // Write-only, prev value irrelevant.

    , [mem] "+Q"  (*dest)    // Read/write, memory to be updated atomically.

    // inputs

    : [upd] "d"   (xchg_val)

    ,       "0"   (cmp_val)  // Read-only, initial value for [old] (operand #0).

    // clobbered

    : "cc", "memory"

  );

  return old;

}

template<>

template<typename T>

inline T Atomic::PlatformCmpxchg<8>::operator()(T xchg_val,

                                                T volatile* dest,

                                                T cmp_val,

                                                atomic_memory_order unused) const {

  STATIC_ASSERT(8 == sizeof(T));

  T old;

  __asm__ __volatile__ (

    "   CSG      %[old],%[upd],%[mem]    \n\t" // Try to xchg upd with mem.

    // outputs

    : [old] "=&d" (old)      // Write-only, prev value irrelevant.

    , [mem] "+Q"  (*dest)    // Read/write, memory to be updated atomically.

    // inputs

    : [upd] "d"   (xchg_val)

    ,       "0"   (cmp_val)  // Read-only, initial value for [old] (operand #0).

    // clobbered

    : "cc", "memory"

  );

  return old;

}

#endif // OS_CPU_LINUX_S390_ATOMIC_LINUX_S390_HPP