/*

 * Copyright (c) 2012, 2018 SAP SE. All rights reserved.

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

 *

 * 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.

 *

 * 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

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 *

 */

#ifndef PPC64

#error "Atomic currently only implemented for PPC64"

#endif

// Implementation of class atomic

//

// machine barrier instructions:

//

// - sync            two-way memory barrier, aka fence

// - lwsync          orders  Store|Store,

//                            Load|Store,

//                            Load|Load,

//                   but not Store|Load

// - eieio           orders memory accesses for device memory (only)

// - isync           invalidates speculatively executed instructions

//                   From the POWER ISA 2.06 documentation:

//                    "[...] an isync instruction prevents the execution of

//                   instructions following the isync until instructions

//                   preceding the isync have completed, [...]"

//                   From IBM's AIX assembler reference:

//                    "The isync [...] instructions causes the processor to

//                   refetch any instructions that might have been fetched

//                   prior to the isync instruction. The instruction isync

//                   causes the processor to wait for all previous instructions

//                   to complete. Then any instructions already fetched are

//                   discarded and instruction processing continues in the

//                   environment established by the previous instructions."

//

// semantic barrier instructions:

// (as defined in orderAccess.hpp)

//

// - release         orders Store|Store,       (maps to lwsync)

//                           Load|Store

// - acquire         orders  Load|Store,       (maps to lwsync)

//                           Load|Load

// - fence           orders Store|Store,       (maps to sync)

//                           Load|Store,

//                           Load|Load,

//                          Store|Load

//

#define strasm_sync                       "\n  sync    \n"

#define strasm_lwsync                     "\n  lwsync  \n"

#define strasm_isync                      "\n  isync   \n"

#define strasm_release                    strasm_lwsync

#define strasm_acquire                    strasm_lwsync

#define strasm_fence                      strasm_sync

#define strasm_nobarrier                  ""

#define strasm_nobarrier_clobber_memory   ""

inline void pre_membar(atomic_memory_order order) {

  switch (order) {

    case memory_order_relaxed:

    case memory_order_acquire: break;

    case memory_order_release:

    case memory_order_acq_rel: __asm__ __volatile__ (strasm_lwsync); break;

    default /*conservative*/ : __asm__ __volatile__ (strasm_sync); break;

  }

}

inline void post_membar(atomic_memory_order order) {

  switch (order) {

    case memory_order_relaxed:

    case memory_order_release: break;

    case memory_order_acquire:

    case memory_order_acq_rel: __asm__ __volatile__ (strasm_isync); break;

    default /*conservative*/ : __asm__ __volatile__ (strasm_sync); break;

  }

}

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 add_value, D volatile* dest,

                                               atomic_memory_order order) const {

  STATIC_ASSERT(4 == sizeof(I));

  STATIC_ASSERT(4 == sizeof(D));

  D result;

  pre_membar(order);

  __asm__ __volatile__ (

    "1: lwarx   %0,  0, %2    \n"

    "   add     %0, %0, %1    \n"

    "   stwcx.  %0,  0, %2    \n"

    "   bne-    1b            \n"

    : /*%0*/"=&r" (result)

    : /*%1*/"r" (add_value), /*%2*/"r" (dest)

    : "cc", "memory" );

  post_membar(order);

  return result;

}

template<>

template<typename I, typename D>

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

                                               atomic_memory_order order) const {

  STATIC_ASSERT(8 == sizeof(I));

  STATIC_ASSERT(8 == sizeof(D));

  D result;

  pre_membar(order);

  __asm__ __volatile__ (

    "1: ldarx   %0,  0, %2    \n"

    "   add     %0, %0, %1    \n"

    "   stdcx.  %0,  0, %2    \n"

    "   bne-    1b            \n"

    : /*%0*/"=&r" (result)

    : /*%1*/"r" (add_value), /*%2*/"r" (dest)

    : "cc", "memory" );

  post_membar(order);

  return result;

}

template<>

template<typename T>

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

                                             T volatile* dest,

                                             atomic_memory_order order) const {

  // Note that xchg doesn't necessarily do an acquire

  // (see synchronizer.cpp).

  T old_value;

  const uint64_t zero = 0;

  pre_membar(order);

  __asm__ __volatile__ (

    /* atomic loop */

    "1:                                                 \n"

    "   lwarx   %[old_value], %[dest], %[zero]          \n"

    "   stwcx.  %[exchange_value], %[dest], %[zero]     \n"

    "   bne-    1b                                      \n"

    /* exit */

    "2:                                                 \n"

    /* out */

    : [old_value]       "=&r"   (old_value),

                        "=m"    (*dest)

    /* in */

    : [dest]            "b"     (dest),

      [zero]            "r"     (zero),

      [exchange_value]  "r"     (exchange_value),

                        "m"     (*dest)

    /* clobber */

    : "cc",

      "memory"

    );

  post_membar(order);

  return old_value;

}

template<>

template<typename T>

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

                                             T volatile* dest,

                                             atomic_memory_order order) const {

  STATIC_ASSERT(8 == sizeof(T));

  // Note that xchg doesn't necessarily do an acquire

  // (see synchronizer.cpp).

  T old_value;

  const uint64_t zero = 0;

  pre_membar(order);

  __asm__ __volatile__ (

    /* atomic loop */

    "1:                                                 \n"

    "   ldarx   %[old_value], %[dest], %[zero]          \n"

    "   stdcx.  %[exchange_value], %[dest], %[zero]     \n"

    "   bne-    1b                                      \n"

    /* exit */

    "2:                                                 \n"

    /* out */

    : [old_value]       "=&r"   (old_value),

                        "=m"    (*dest)

    /* in */

    : [dest]            "b"     (dest),

      [zero]            "r"     (zero),

      [exchange_value]  "r"     (exchange_value),

                        "m"     (*dest)

    /* clobber */

    : "cc",

      "memory"

    );

  post_membar(order);

  return old_value;

}

template<>

template<typename T>

inline T Atomic::PlatformCmpxchg<1>::operator()(T exchange_value,

                                                T volatile* dest,

                                                T compare_value,

                                                atomic_memory_order order) const {

  STATIC_ASSERT(1 == sizeof(T));

  // Note that cmpxchg guarantees a two-way memory barrier across

  // the cmpxchg, so it's really a a 'fence_cmpxchg_fence' if not

  // specified otherwise (see atomic.hpp).

  // Using 32 bit internally.

  volatile int *dest_base = (volatile int*)((uintptr_t)dest & ~3);

#ifdef VM_LITTLE_ENDIAN

  const unsigned int shift_amount        = ((uintptr_t)dest & 3) * 8;

#else

  const unsigned int shift_amount        = ((~(uintptr_t)dest) & 3) * 8;

#endif

  const unsigned int masked_compare_val  = ((unsigned int)(unsigned char)compare_value),

                     masked_exchange_val = ((unsigned int)(unsigned char)exchange_value),

                     xor_value           = (masked_compare_val ^ masked_exchange_val) << shift_amount;

  unsigned int old_value, value32;

  pre_membar(order);

  __asm__ __volatile__ (

    /* simple guard */

    "   lbz     %[old_value], 0(%[dest])                  \n"

    "   cmpw    %[masked_compare_val], %[old_value]       \n"

    "   bne-    2f                                        \n"

    /* atomic loop */

    "1:                                                   \n"

    "   lwarx   %[value32], 0, %[dest_base]               \n"

    /* extract byte and compare */

    "   srd     %[old_value], %[value32], %[shift_amount] \n"

    "   clrldi  %[old_value], %[old_value], 56            \n"

    "   cmpw    %[masked_compare_val], %[old_value]       \n"

    "   bne-    2f                                        \n"

    /* replace byte and try to store */

    "   xor     %[value32], %[xor_value], %[value32]      \n"

    "   stwcx.  %[value32], 0, %[dest_base]               \n"

    "   bne-    1b                                        \n"

    /* exit */

    "2:                                                   \n"

    /* out */

    : [old_value]           "=&r"   (old_value),

      [value32]             "=&r"   (value32),

                            "=m"    (*dest),

                            "=m"    (*dest_base)

    /* in */

    : [dest]                "b"     (dest),

      [dest_base]           "b"     (dest_base),

      [shift_amount]        "r"     (shift_amount),

      [masked_compare_val]  "r"     (masked_compare_val),

      [xor_value]           "r"     (xor_value),

                            "m"     (*dest),

                            "m"     (*dest_base)

    /* clobber */

    : "cc",

      "memory"

    );

  post_membar(order);

  return PrimitiveConversions::cast<T>((unsigned char)old_value);

}

template<>

template<typename T>

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

                                                T volatile* dest,

                                                T compare_value,

                                                atomic_memory_order order) const {

  STATIC_ASSERT(4 == sizeof(T));

  // Note that cmpxchg guarantees a two-way memory barrier across

  // the cmpxchg, so it's really a a 'fence_cmpxchg_fence' if not

  // specified otherwise (see atomic.hpp).

  T old_value;

  const uint64_t zero = 0;

  pre_membar(order);

  __asm__ __volatile__ (

    /* simple guard */

    "   lwz     %[old_value], 0(%[dest])                \n"

    "   cmpw    %[compare_value], %[old_value]          \n"

    "   bne-    2f                                      \n"

    /* atomic loop */

    "1:                                                 \n"

    "   lwarx   %[old_value], %[dest], %[zero]          \n"

    "   cmpw    %[compare_value], %[old_value]          \n"

    "   bne-    2f                                      \n"

    "   stwcx.  %[exchange_value], %[dest], %[zero]     \n"

    "   bne-    1b                                      \n"

    /* exit */

    "2:                                                 \n"

    /* out */

    : [old_value]       "=&r"   (old_value),

                        "=m"    (*dest)

    /* in */

    : [dest]            "b"     (dest),

      [zero]            "r"     (zero),

      [compare_value]   "r"     (compare_value),

      [exchange_value]  "r"     (exchange_value),

                        "m"     (*dest)

    /* clobber */

    : "cc",

      "memory"

    );

  post_membar(order);

  return old_value;

}

template<>

template<typename T>

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

                                                T volatile* dest,

                                                T compare_value,

                                                atomic_memory_order order) const {

  STATIC_ASSERT(8 == sizeof(T));

  // Note that cmpxchg guarantees a two-way memory barrier across

  // the cmpxchg, so it's really a a 'fence_cmpxchg_fence' if not

  // specified otherwise (see atomic.hpp).

  T old_value;

  const uint64_t zero = 0;

  pre_membar(order);

  __asm__ __volatile__ (

    /* simple guard */

    "   ld      %[old_value], 0(%[dest])                \n"

    "   cmpd    %[compare_value], %[old_value]          \n"

    "   bne-    2f                                      \n"

    /* atomic loop */

    "1:                                                 \n"

    "   ldarx   %[old_value], %[dest], %[zero]          \n"

    "   cmpd    %[compare_value], %[old_value]          \n"

    "   bne-    2f                                      \n"

    "   stdcx.  %[exchange_value], %[dest], %[zero]     \n"

    "   bne-    1b                                      \n"

    /* exit */

    "2:                                                 \n"

    /* out */

    : [old_value]       "=&r"   (old_value),

                        "=m"    (*dest)

    /* in */

    : [dest]            "b"     (dest),

      [zero]            "r"     (zero),

      [compare_value]   "r"     (compare_value),

      [exchange_value]  "r"     (exchange_value),

                        "m"     (*dest)

    /* clobber */

    : "cc",

      "memory"

    );

  post_membar(order);

  return old_value;

}

#undef strasm_sync

#undef strasm_lwsync

#undef strasm_isync

#undef strasm_release

#undef strasm_acquire

#undef strasm_fence

#undef strasm_nobarrier

#undef strasm_nobarrier_clobber_memory