/*

 Package: dyncall
 Library: dyncallback
 File: dyncallback/dyncall_args_x64.c
 Description: Callback's Arguments VM - Implementation for x64
 License:

   Copyright (c) 2007-2022 Daniel Adler <dadler@uni-goettingen.de>,
                           Tassilo Philipp <tphilipp@potion-studios.com>

   Permission to use, copy, modify, and distribute this software for any
   purpose with or without fee is hereby granted, provided that the above
   copyright notice and this permission notice appear in all copies.

   THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
   WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
   MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
   ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
   WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
   ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
   OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

*/



#include "dyncall_args_x64.h"

#include <assert.h>
#include <string.h>


static int64* arg_i64(DCArgs* args)
{
  args->reg_count.i += (args->reg_count.i == args->aggr_return_register);

  if (args->reg_count.i < numIntRegs)
    return &args->reg_data.i[args->reg_count.i++];
  else
    return args->stack_ptr++;
}


static double* arg_f64(DCArgs* args)
{
#if defined(DC_WINDOWS)
  args->reg_count.f += (args->reg_count.f == args->aggr_return_register);
#endif
  if (args->reg_count.f < numFloatRegs)
    return &args->reg_data.f[args->reg_count.f++];
  else
    return (double*)args->stack_ptr++;
}



DClonglong  dcbArgLongLong (DCArgs* p) { return *arg_i64(p); }
DCint       dcbArgInt      (DCArgs* p) { return (int)   dcbArgLongLong(p); }
DClong      dcbArgLong     (DCArgs* p) { return (long)  dcbArgLongLong(p); }
DCchar      dcbArgChar     (DCArgs* p) { return (char)  dcbArgLongLong(p); }
DCshort     dcbArgShort    (DCArgs* p) { return (short) dcbArgLongLong(p); }
DCbool      dcbArgBool     (DCArgs* p) { return dcbArgInt(p) != 0; }

DCuint      dcbArgUInt     (DCArgs* p) { return (DCuint)      dcbArgInt(p);      }
DCuchar     dcbArgUChar    (DCArgs* p) { return (DCuchar)     dcbArgChar(p);     }
DCushort    dcbArgUShort   (DCArgs* p) { return (DCushort)    dcbArgShort(p);    }
DCulong     dcbArgULong    (DCArgs* p) { return (DCulong)     dcbArgLong(p);     }
DCulonglong dcbArgULongLong(DCArgs* p) { return (DCulonglong) dcbArgLongLong(p); }


DCpointer   dcbArgPointer  (DCArgs* p) { return (DCpointer)   dcbArgLongLong(p); }

DCdouble    dcbArgDouble   (DCArgs* p) { return *arg_f64(p); }
DCfloat     dcbArgFloat    (DCArgs* p) { return *(float*)arg_f64(p); }

void        dcbArgAggr     (DCArgs* p, DCpointer target)
{
  int i;
  DCaggr *ag = *(p->aggrs++);

  if(!ag) {
    /* non-trivial aggr: pass as ptr, user was supposed to make copy */
    dcbArgPointer(target);
    return;
  }

#if defined(DC_UNIX)
  DCRegCount_x64 n_regs = { p->reg_count.i, p->reg_count.f };

  if(ag->sysv_classes[0] != SYSVC_MEMORY) {
    /* reclassify aggr w/ respect to remaining regs, might have been passed entirely via the stack */
    for(i=0; ag->sysv_classes[i] && i<DC_SYSV_MAX_NUM_CLASSES; ++i) {
      DCuchar clz = ag->sysv_classes[i];
      n_regs.i += (clz == SYSVC_INTEGER);
      n_regs.f += (clz == SYSVC_SSE);
      /* @@@AGGR implement when implementing x87 types */
    }
  }

  if(ag->sysv_classes[0] == SYSVC_MEMORY || (n_regs.i > numIntRegs) || (n_regs.f > numFloatRegs))
  {
     memcpy(target, p->stack_ptr, ag->size);
     p->stack_ptr = p->stack_ptr + ((ag->size + (sizeof(DClonglong)-1)) >> 3); // advance to next full stack slot
     return;
  }


  for(i=0; ag->sysv_classes[i] && i<DC_SYSV_MAX_NUM_CLASSES; ++i)
  {
    switch (ag->sysv_classes[i])
    {
      case SYSVC_INTEGER: ((DClonglong*)target)[i] = dcbArgLongLong(p); break;
      case SYSVC_SSE:     ((DCdouble  *)target)[i] = dcbArgDouble  (p); break;
      /* @@@AGGR implement when implementing x87 types */
      default:
          assert(DC_FALSE && "Should never be reached because we check for unupported classes earlier");
    }
  }

#else

  switch (ag->size) {
    case 1: *(DCchar    *)target = dcbArgChar    (p); break;
    case 2: *(DCshort   *)target = dcbArgShort   (p); break;
    case 4: *(DClong    *)target = dcbArgLong    (p); break;
    case 8: *(DClonglong*)target = dcbArgLongLong(p); break;
    default: memcpy(target, dcbArgPointer(p), ag->size); break;
  }
#endif
}


/* A 16 byte struct would be sufficient for System V (because at most two of the four registers can be full). */
/* But then it's much more complicated to copy the result to the correct registers in assembly. */
typedef struct {
  DClonglong r[2]; /* rax, rdx   */
  DCdouble   x[2]; /* xmm0, xmm1 */
} DCRetRegs_SysV;

void dcbReturnAggr(DCArgs *args, DCValue *result, DCpointer ret)
{
  int i;
  DCaggr *ag = *(args->aggrs++);

  if (args->aggr_return_register >= 0) {
    DCpointer dest = (DCpointer) args->reg_data.i[args->aggr_return_register];
    memcpy(dest, ret, ag->size);
    result->p = dest;
  } else {
#if defined(DC_UNIX)
    /* a max of 2 regs are used in this case, out of rax, rdx, xmm0 and xmm1 */
    /* space for 4 qwords is pointed to by (DCRetRegs_SysV*)result */
    DClonglong *intRegs = ((DCRetRegs_SysV*)result)->r;
    DCdouble   *sseRegs = ((DCRetRegs_SysV*)result)->x;
    for(i=0; ag->sysv_classes[i] && i<2/*guaranteed*/; ++i) {
      switch (ag->sysv_classes[i]) {
        case SYSVC_INTEGER: *(intRegs++) = ((DClonglong*)ret)[i]; break;
        case SYSVC_SSE:     *(sseRegs++) = ((DCdouble  *)ret)[i]; break;
        /* @@@AGGR implement when implementing x87 types, might lead to more than 2 regs (e.g. _m512) */
        default: assert(DC_FALSE && "Should never be reached because we check for unupported classes earlier");
      }
    }
#else
    /* copy aggregate (guaranteed to be <= 8b by call conv, as no hidden ptr) into result */
    assert(ag->size <= 8 && "aggregate info mismatch for return type");
    memcpy(result, ret, ag->size);
#endif
  }
}