ffi_sysv.c

/* -----------------------------------------------------------------------
   ffi_sysv.c - Copyright (C) 2013 IBM
                Copyright (C) 2011 Anthony Green
                Copyright (C) 2011 Kyle Moffett
                Copyright (C) 2008 Red Hat, Inc
                Copyright (C) 2007, 2008 Free Software Foundation, Inc
                Copyright (c) 1998 Geoffrey Keating

   PowerPC Foreign Function Interface

   Permission is hereby granted, free of charge, to any person obtaining
   a copy of this software and associated documentation files (the
   ``Software''), to deal in the Software without restriction, including
   without limitation the rights to use, copy, modify, merge, publish,
   distribute, sublicense, and/or sell copies of the Software, and to
   permit persons to whom the Software is furnished to do so, subject to
   the following conditions:

   The above copyright notice and this permission notice shall be included
   in all copies or substantial portions of the Software.

   THE SOFTWARE IS PROVIDED ``AS IS'', WITHOUT WARRANTY OF ANY KIND, EXPRESS
   OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
   MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
   IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY CLAIM, DAMAGES OR
   OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
   ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
   OTHER DEALINGS IN THE SOFTWARE.
   ----------------------------------------------------------------------- */

#include "ffi.h"

#ifndef POWERPC64
#include "ffi_common.h"
#include "ffi_powerpc.h"


/* About the SYSV ABI.  */
#define ASM_NEEDS_REGISTERS 6
#define NUM_GPR_ARG_REGISTERS 8
#define NUM_FPR_ARG_REGISTERS 8


#if HAVE_LONG_DOUBLE_VARIANT && FFI_TYPE_LONGDOUBLE != FFI_TYPE_DOUBLE
/* Adjust size of ffi_type_longdouble.  */
void FFI_HIDDEN
ffi_prep_types_sysv (ffi_abi abi)
{
  if ((abi & (FFI_SYSV | FFI_SYSV_LONG_DOUBLE_128)) == FFI_SYSV)
    {
      ffi_type_longdouble.size = 8;
      ffi_type_longdouble.alignment = 8;
    }
  else
    {
      ffi_type_longdouble.size = 16;
      ffi_type_longdouble.alignment = 16;
    }
}
#endif

/* Transform long double, double and float to other types as per abi.  */
static int
translate_float (int abi, int type)
{
#if FFI_TYPE_LONGDOUBLE != FFI_TYPE_DOUBLE
  if (type == FFI_TYPE_LONGDOUBLE
      && (abi & FFI_SYSV_LONG_DOUBLE_128) == 0)
    type = FFI_TYPE_DOUBLE;
#endif
  if ((abi & FFI_SYSV_SOFT_FLOAT) != 0)
    {
      if (type == FFI_TYPE_FLOAT)
	type = FFI_TYPE_UINT32;
      else if (type == FFI_TYPE_DOUBLE)
	type = FFI_TYPE_UINT64;
#if FFI_TYPE_LONGDOUBLE != FFI_TYPE_DOUBLE
      else if (type == FFI_TYPE_LONGDOUBLE)
	type = FFI_TYPE_UINT128;
    }
  else if ((abi & FFI_SYSV_IBM_LONG_DOUBLE) == 0)
    {
      if (type == FFI_TYPE_LONGDOUBLE)
	type = FFI_TYPE_STRUCT;
#endif
    }
  return type;
}

/* Perform machine dependent cif processing */
static ffi_status
ffi_prep_cif_sysv_core (ffi_cif *cif)
{
  ffi_type **ptr;
  unsigned bytes;
  unsigned i, fparg_count = 0, intarg_count = 0;
  unsigned flags = cif->flags;
  unsigned struct_copy_size = 0;
  unsigned type = cif->rtype->type;
  unsigned size = cif->rtype->size;

  /* The machine-independent calculation of cif->bytes doesn't work
     for us.  Redo the calculation.  */

  /* Space for the frame pointer, callee's LR, and the asm's temp regs.  */
  bytes = (2 + ASM_NEEDS_REGISTERS) * sizeof (int);

  /* Space for the GPR registers.  */
  bytes += NUM_GPR_ARG_REGISTERS * sizeof (int);

  /* Return value handling.  The rules for SYSV are as follows:
     - 32-bit (or less) integer values are returned in gpr3;
     - Structures of size <= 4 bytes also returned in gpr3;
     - 64-bit integer values and structures between 5 and 8 bytes are returned
     in gpr3 and gpr4;
     - Larger structures are allocated space and a pointer is passed as
     the first argument.
     - Single/double FP values are returned in fpr1;
     - long doubles (if not equivalent to double) are returned in
     fpr1,fpr2 for Linux and as for large structs for SysV.  */

  type = translate_float (cif->abi, type);

  switch (type)
    {
#if FFI_TYPE_LONGDOUBLE != FFI_TYPE_DOUBLE
    case FFI_TYPE_LONGDOUBLE:
      flags |= FLAG_RETURNS_128BITS;
      /* Fall through.  */
#endif
    case FFI_TYPE_DOUBLE:
      flags |= FLAG_RETURNS_64BITS;
      /* Fall through.  */
    case FFI_TYPE_FLOAT:
      flags |= FLAG_RETURNS_FP;
#ifdef __NO_FPRS__
      return FFI_BAD_ABI;
#endif
      break;

    case FFI_TYPE_UINT128:
      flags |= FLAG_RETURNS_128BITS;
      /* Fall through.  */
    case FFI_TYPE_UINT64:
    case FFI_TYPE_SINT64:
      flags |= FLAG_RETURNS_64BITS;
      break;

    case FFI_TYPE_STRUCT:
      /* The final SYSV ABI says that structures smaller or equal 8 bytes
	 are returned in r3/r4.  A draft ABI used by linux instead
	 returns them in memory.  */
      if ((cif->abi & FFI_SYSV_STRUCT_RET) != 0 && size <= 8)
	{
	  flags |= FLAG_RETURNS_SMST;
	  break;
	}
      intarg_count++;
      flags |= FLAG_RETVAL_REFERENCE;
      /* Fall through.  */
    case FFI_TYPE_VOID:
      flags |= FLAG_RETURNS_NOTHING;
      break;

    default:
      /* Returns 32-bit integer, or similar.  Nothing to do here.  */
      break;
    }

  /* The first NUM_GPR_ARG_REGISTERS words of integer arguments, and the
     first NUM_FPR_ARG_REGISTERS fp arguments, go in registers; the rest
     goes on the stack.  Structures and long doubles (if not equivalent
     to double) are passed as a pointer to a copy of the structure.
     Stuff on the stack needs to keep proper alignment.  */
  for (ptr = cif->arg_types, i = cif->nargs; i > 0; i--, ptr++)
    {
      unsigned short typenum = (*ptr)->type;

      typenum = translate_float (cif->abi, typenum);

      switch (typenum)
	{
#if FFI_TYPE_LONGDOUBLE != FFI_TYPE_DOUBLE
	case FFI_TYPE_LONGDOUBLE:
	  fparg_count++;
	  /* Fall thru */
#endif
	case FFI_TYPE_DOUBLE:
	  fparg_count++;
	  /* If this FP arg is going on the stack, it must be
	     8-byte-aligned.  */
	  if (fparg_count > NUM_FPR_ARG_REGISTERS
	      && intarg_count >= NUM_GPR_ARG_REGISTERS
	      && intarg_count % 2 != 0)
	    intarg_count++;
#ifdef __NO_FPRS__
	  return FFI_BAD_ABI;
#endif
	  break;

	case FFI_TYPE_FLOAT:
	  fparg_count++;
#ifdef __NO_FPRS__
	  return FFI_BAD_ABI;
#endif
	  break;

	case FFI_TYPE_UINT128:
	  /* A long double in FFI_LINUX_SOFT_FLOAT can use only a set
	     of four consecutive gprs. If we do not have enough, we
	     have to adjust the intarg_count value.  */
	  if (intarg_count >= NUM_GPR_ARG_REGISTERS - 3
	      && intarg_count < NUM_GPR_ARG_REGISTERS)
	    intarg_count = NUM_GPR_ARG_REGISTERS;
	  intarg_count += 4;
	  break;

	case FFI_TYPE_UINT64:
	case FFI_TYPE_SINT64:
	  /* 'long long' arguments are passed as two words, but
	     either both words must fit in registers or both go
	     on the stack.  If they go on the stack, they must
	     be 8-byte-aligned.

	     Also, only certain register pairs can be used for
	     passing long long int -- specifically (r3,r4), (r5,r6),
	     (r7,r8), (r9,r10).  */
	  if (intarg_count == NUM_GPR_ARG_REGISTERS-1
	      || intarg_count % 2 != 0)
	    intarg_count++;
	  intarg_count += 2;
	  break;

	case FFI_TYPE_STRUCT:
	  /* We must allocate space for a copy of these to enforce
	     pass-by-value.  Pad the space up to a multiple of 16
	     bytes (the maximum alignment required for anything under
	     the SYSV ABI).  */
	  struct_copy_size += ((*ptr)->size + 15) & ~0xF;
	  /* Fall through (allocate space for the pointer).  */

	case FFI_TYPE_POINTER:
	case FFI_TYPE_INT:
	case FFI_TYPE_UINT32:
	case FFI_TYPE_SINT32:
	case FFI_TYPE_UINT16:
	case FFI_TYPE_SINT16:
	case FFI_TYPE_UINT8:
	case FFI_TYPE_SINT8:
	  /* Everything else is passed as a 4-byte word in a GPR, either
	     the object itself or a pointer to it.  */
	  intarg_count++;
	  break;

	default:
	  FFI_ASSERT (0);
	}
    }

  if (fparg_count != 0)
    flags |= FLAG_FP_ARGUMENTS;
  if (intarg_count > 4)
    flags |= FLAG_4_GPR_ARGUMENTS;
  if (struct_copy_size != 0)
    flags |= FLAG_ARG_NEEDS_COPY;

  /* Space for the FPR registers, if needed.  */
  if (fparg_count != 0)
    bytes += NUM_FPR_ARG_REGISTERS * sizeof (double);

  /* Stack space.  */
  if (intarg_count > NUM_GPR_ARG_REGISTERS)
    bytes += (intarg_count - NUM_GPR_ARG_REGISTERS) * sizeof (int);
  if (fparg_count > NUM_FPR_ARG_REGISTERS)
    bytes += (fparg_count - NUM_FPR_ARG_REGISTERS) * sizeof (double);

  /* The stack space allocated needs to be a multiple of 16 bytes.  */
  bytes = (bytes + 15) & ~0xF;

  /* Add in the space for the copied structures.  */
  bytes += struct_copy_size;

  cif->flags = flags;
  cif->bytes = bytes;

  return FFI_OK;
}

ffi_status FFI_HIDDEN
ffi_prep_cif_sysv (ffi_cif *cif)
{
  if ((cif->abi & FFI_SYSV) == 0)
    {
      /* This call is from old code.  Translate to new ABI values.  */
      cif->flags |= FLAG_COMPAT;
      switch (cif->abi)
	{
	default:
	  return FFI_BAD_ABI;

	case FFI_COMPAT_SYSV:
	  cif->abi = FFI_SYSV | FFI_SYSV_STRUCT_RET | FFI_SYSV_LONG_DOUBLE_128;
	  break;

	case FFI_COMPAT_GCC_SYSV:
	  cif->abi = FFI_SYSV | FFI_SYSV_LONG_DOUBLE_128;
	  break;

	case FFI_COMPAT_LINUX:
	  cif->abi = (FFI_SYSV | FFI_SYSV_IBM_LONG_DOUBLE
		      | FFI_SYSV_LONG_DOUBLE_128);
	  break;

	case FFI_COMPAT_LINUX_SOFT_FLOAT:
	  cif->abi = (FFI_SYSV | FFI_SYSV_SOFT_FLOAT | FFI_SYSV_IBM_LONG_DOUBLE
		      | FFI_SYSV_LONG_DOUBLE_128);
	  break;
	}
    }
  return ffi_prep_cif_sysv_core (cif);
}

/* ffi_prep_args_SYSV is called by the assembly routine once stack space
   has been allocated for the function's arguments.

   The stack layout we want looks like this:

   |   Return address from ffi_call_SYSV 4bytes	|	higher addresses
   |--------------------------------------------|
   |   Previous backchain pointer	4	|       stack pointer here
   |--------------------------------------------|<+ <<<	on entry to
   |   Saved r28-r31			4*4	| |	ffi_call_SYSV
   |--------------------------------------------| |
   |   GPR registers r3-r10		8*4	| |	ffi_call_SYSV
   |--------------------------------------------| |
   |   FPR registers f1-f8 (optional)	8*8	| |
   |--------------------------------------------| |	stack	|
   |   Space for copied structures		| |	grows	|
   |--------------------------------------------| |	down    V
   |   Parameters that didn't fit in registers  | |
   |--------------------------------------------| |	lower addresses
   |   Space for callee's LR		4	| |
   |--------------------------------------------| |	stack pointer here
   |   Current backchain pointer	4	|-/	during
   |--------------------------------------------|   <<<	ffi_call_SYSV

*/

void FFI_HIDDEN
ffi_prep_args_SYSV (extended_cif *ecif, unsigned *const stack)
{
  const unsigned bytes = ecif->cif->bytes;
  const unsigned flags = ecif->cif->flags;

  typedef union
  {
    char *c;
    unsigned *u;
    long long *ll;
    float *f;
    double *d;
  } valp;

  /* 'stacktop' points at the previous backchain pointer.  */
  valp stacktop;

  /* 'gpr_base' points at the space for gpr3, and grows upwards as
     we use GPR registers.  */
  valp gpr_base;
  int intarg_count;

#ifndef __NO_FPRS__
  /* 'fpr_base' points at the space for fpr1, and grows upwards as
     we use FPR registers.  */
  valp fpr_base;
  int fparg_count;
#endif

  /* 'copy_space' grows down as we put structures in it.  It should
     stay 16-byte aligned.  */
  valp copy_space;

  /* 'next_arg' grows up as we put parameters in it.  */
  valp next_arg;

  int i;
  ffi_type **ptr;
#ifndef __NO_FPRS__
  double double_tmp;
#endif
  union
  {
    void **v;
    char **c;
    signed char **sc;
    unsigned char **uc;
    signed short **ss;
    unsigned short **us;
    unsigned int **ui;
    long long **ll;
    float **f;
    double **d;
  } p_argv;
  size_t struct_copy_size;
  unsigned gprvalue;

  stacktop.c = (char *) stack + bytes;
  gpr_base.u = stacktop.u - ASM_NEEDS_REGISTERS - NUM_GPR_ARG_REGISTERS;
  intarg_count = 0;
#ifndef __NO_FPRS__
  fpr_base.d = gpr_base.d - NUM_FPR_ARG_REGISTERS;
  fparg_count = 0;
  copy_space.c = ((flags & FLAG_FP_ARGUMENTS) ? fpr_base.c : gpr_base.c);
#else
  copy_space.c = gpr_base.c;
#endif
  next_arg.u = stack + 2;

  /* Check that everything starts aligned properly.  */
  FFI_ASSERT (((unsigned long) (char *) stack & 0xF) == 0);
  FFI_ASSERT (((unsigned long) copy_space.c & 0xF) == 0);
  FFI_ASSERT (((unsigned long) stacktop.c & 0xF) == 0);
  FFI_ASSERT ((bytes & 0xF) == 0);
  FFI_ASSERT (copy_space.c >= next_arg.c);

  /* Deal with return values that are actually pass-by-reference.  */
  if (flags & FLAG_RETVAL_REFERENCE)
    {
      *gpr_base.u++ = (unsigned long) (char *) ecif->rvalue;
      intarg_count++;
    }

  /* Now for the arguments.  */
  p_argv.v = ecif->avalue;
  for (ptr = ecif->cif->arg_types, i = ecif->cif->nargs;
       i > 0;
       i--, ptr++, p_argv.v++)
    {
      unsigned int typenum = (*ptr)->type;

      typenum = translate_float (ecif->cif->abi, typenum);

      /* Now test the translated value */
      switch (typenum)
	{
#ifndef __NO_FPRS__
# if FFI_TYPE_LONGDOUBLE != FFI_TYPE_DOUBLE
	case FFI_TYPE_LONGDOUBLE:
	  double_tmp = (*p_argv.d)[0];

	  if (fparg_count >= NUM_FPR_ARG_REGISTERS - 1)
	    {
	      if (intarg_count >= NUM_GPR_ARG_REGISTERS
		  && intarg_count % 2 != 0)
		{
		  intarg_count++;
		  next_arg.u++;
		}
	      *next_arg.d = double_tmp;
	      next_arg.u += 2;
	      double_tmp = (*p_argv.d)[1];
	      *next_arg.d = double_tmp;
	      next_arg.u += 2;
	    }
	  else
	    {
	      *fpr_base.d++ = double_tmp;
	      double_tmp = (*p_argv.d)[1];
	      *fpr_base.d++ = double_tmp;
	    }

	  fparg_count += 2;
	  FFI_ASSERT (flags & FLAG_FP_ARGUMENTS);
	  break;
# endif
	case FFI_TYPE_DOUBLE:
	  double_tmp = **p_argv.d;

	  if (fparg_count >= NUM_FPR_ARG_REGISTERS)
	    {
	      if (intarg_count >= NUM_GPR_ARG_REGISTERS
		  && intarg_count % 2 != 0)
		{
		  intarg_count++;
		  next_arg.u++;
		}
	      *next_arg.d = double_tmp;
	      next_arg.u += 2;
	    }
	  else
	    *fpr_base.d++ = double_tmp;
	  fparg_count++;
	  FFI_ASSERT (flags & FLAG_FP_ARGUMENTS);
	  break;

	case FFI_TYPE_FLOAT:
	  double_tmp = **p_argv.f;
	  if (fparg_count >= NUM_FPR_ARG_REGISTERS)
	    {
	      *next_arg.f = (float) double_tmp;
	      next_arg.u += 1;
	      intarg_count++;
	    }
	  else
	    *fpr_base.d++ = double_tmp;
	  fparg_count++;
	  FFI_ASSERT (flags & FLAG_FP_ARGUMENTS);
	  break;
#endif /* have FPRs */

	case FFI_TYPE_UINT128:
	  /* The soft float ABI for long doubles works like this, a long double
	     is passed in four consecutive GPRs if available.  A maximum of 2
	     long doubles can be passed in gprs.  If we do not have 4 GPRs
	     left, the long double is passed on the stack, 4-byte aligned.  */
	  {
	    unsigned int int_tmp;
	    unsigned int ii;
	    if (intarg_count >= NUM_GPR_ARG_REGISTERS - 3)
	      {
		if (intarg_count < NUM_GPR_ARG_REGISTERS)
		  intarg_count = NUM_GPR_ARG_REGISTERS;
		for (ii = 0; ii < 4; ii++)
		  {
		    int_tmp = (*p_argv.ui)[ii];
		    *next_arg.u++ = int_tmp;
		  }
	      }
	    else
	      {
		for (ii = 0; ii < 4; ii++)
		  {
		    int_tmp = (*p_argv.ui)[ii];
		    *gpr_base.u++ = int_tmp;
		  }
	      }
	    intarg_count += 4;
	    break;
	  }

	case FFI_TYPE_UINT64:
	case FFI_TYPE_SINT64:
	  if (intarg_count == NUM_GPR_ARG_REGISTERS-1)
	    intarg_count++;
	  if (intarg_count >= NUM_GPR_ARG_REGISTERS)
	    {
	      if (intarg_count % 2 != 0)
		{
		  intarg_count++;
		  next_arg.u++;
		}
	      *next_arg.ll = **p_argv.ll;
	      next_arg.u += 2;
	    }
	  else
	    {
	      /* The abi states only certain register pairs can be
		 used for passing long long int specifically (r3,r4),
		 (r5,r6), (r7,r8), (r9,r10).  If next arg is long long
		 but not correct starting register of pair then skip
		 until the proper starting register.  */
	      if (intarg_count % 2 != 0)
		{
		  intarg_count ++;
		  gpr_base.u++;
		}
	      *gpr_base.ll++ = **p_argv.ll;
	    }
	  intarg_count += 2;
	  break;

	case FFI_TYPE_STRUCT:
	  struct_copy_size = ((*ptr)->size + 15) & ~0xF;
	  copy_space.c -= struct_copy_size;
	  memcpy (copy_space.c, *p_argv.c, (*ptr)->size);

	  gprvalue = (unsigned long) copy_space.c;

	  FFI_ASSERT (copy_space.c > next_arg.c);
	  FFI_ASSERT (flags & FLAG_ARG_NEEDS_COPY);
	  goto putgpr;

	case FFI_TYPE_UINT8:
	  gprvalue = **p_argv.uc;
	  goto putgpr;
	case FFI_TYPE_SINT8:
	  gprvalue = **p_argv.sc;
	  goto putgpr;
	case FFI_TYPE_UINT16:
	  gprvalue = **p_argv.us;
	  goto putgpr;
	case FFI_TYPE_SINT16:
	  gprvalue = **p_argv.ss;
	  goto putgpr;

	case FFI_TYPE_INT:
	case FFI_TYPE_UINT32:
	case FFI_TYPE_SINT32:
	case FFI_TYPE_POINTER:

	  gprvalue = **p_argv.ui;

	putgpr:
	  if (intarg_count >= NUM_GPR_ARG_REGISTERS)
	    *next_arg.u++ = gprvalue;
	  else
	    *gpr_base.u++ = gprvalue;
	  intarg_count++;
	  break;
	}
    }

  /* Check that we didn't overrun the stack...  */
  FFI_ASSERT (copy_space.c >= next_arg.c);
  FFI_ASSERT (gpr_base.u <= stacktop.u - ASM_NEEDS_REGISTERS);
  /* The assert below is testing that the number of integer arguments agrees
     with the number found in ffi_prep_cif_machdep().  However, intarg_count
     is incremented whenever we place an FP arg on the stack, so account for
     that before our assert test.  */
#ifndef __NO_FPRS__
  if (fparg_count > NUM_FPR_ARG_REGISTERS)
    intarg_count -= fparg_count - NUM_FPR_ARG_REGISTERS;
  FFI_ASSERT (fpr_base.u
	      <= stacktop.u - ASM_NEEDS_REGISTERS - NUM_GPR_ARG_REGISTERS);
#endif
  FFI_ASSERT (flags & FLAG_4_GPR_ARGUMENTS || intarg_count <= 4);
}

#define MIN_CACHE_LINE_SIZE 8

static void
flush_icache (char *wraddr, char *xaddr, int size)
{
  int i;
  for (i = 0; i < size; i += MIN_CACHE_LINE_SIZE)
    __asm__ volatile ("icbi 0,%0;" "dcbf 0,%1;"
		      : : "r" (xaddr + i), "r" (wraddr + i) : "memory");
  __asm__ volatile ("icbi 0,%0;" "dcbf 0,%1;" "sync;" "isync;"
		    : : "r"(xaddr + size - 1), "r"(wraddr + size - 1)
		    : "memory");
}

ffi_status FFI_HIDDEN
ffi_prep_closure_loc_sysv (ffi_closure *closure,
			   ffi_cif *cif,
			   void (*fun) (ffi_cif *, void *, void **, void *),
			   void *user_data,
			   void *codeloc)
{
  unsigned int *tramp;

  if (cif->abi < FFI_SYSV || cif->abi >= FFI_LAST_ABI)
    return FFI_BAD_ABI;

  tramp = (unsigned int *) &closure->tramp[0];
  tramp[0] = 0x7c0802a6;  /*   mflr    r0 */
  tramp[1] = 0x429f0005;  /*   bcl     20,31,.+4 */
  tramp[2] = 0x7d6802a6;  /*   mflr    r11 */
  tramp[3] = 0x7c0803a6;  /*   mtlr    r0 */
  tramp[4] = 0x800b0018;  /*   lwz     r0,24(r11) */
  tramp[5] = 0x816b001c;  /*   lwz     r11,28(r11) */
  tramp[6] = 0x7c0903a6;  /*   mtctr   r0 */
  tramp[7] = 0x4e800420;  /*   bctr */
  *(void **) &tramp[8] = (void *) ffi_closure_SYSV; /* function */
  *(void **) &tramp[9] = codeloc;                   /* context */

  /* Flush the icache.  */
  flush_icache ((char *)tramp, (char *)codeloc, 8 * 4);

  closure->cif = cif;
  closure->fun = fun;
  closure->user_data = user_data;

  return FFI_OK;
}

/* Basically the trampoline invokes ffi_closure_SYSV, and on
   entry, r11 holds the address of the closure.
   After storing the registers that could possibly contain
   parameters to be passed into the stack frame and setting
   up space for a return value, ffi_closure_SYSV invokes the
   following helper function to do most of the work.  */

int
ffi_closure_helper_SYSV (ffi_cif *cif,
			 void (*fun) (ffi_cif *, void *, void **, void *),
			 void *user_data,
			 void *rvalue,
			 unsigned long *pgr,
			 ffi_dblfl *pfr,
			 unsigned long *pst)
{
  /* rvalue is the pointer to space for return value in closure assembly */
  /* pgr is the pointer to where r3-r10 are stored in ffi_closure_SYSV */
  /* pfr is the pointer to where f1-f8 are stored in ffi_closure_SYSV  */
  /* pst is the pointer to outgoing parameter stack in original caller */

  void **          avalue;
  ffi_type **      arg_types;
  long             i, avn;
#ifndef __NO_FPRS__
  long             nf = 0;   /* number of floating registers already used */
#endif
  long             ng = 0;   /* number of general registers already used */

  unsigned       size     = cif->rtype->size;
  unsigned short rtypenum = cif->rtype->type;

  avalue = alloca (cif->nargs * sizeof (void *));

  /* First translate for softfloat/nonlinux */
  rtypenum = translate_float (cif->abi, rtypenum);

  /* Copy the caller's structure return value address so that the closure
     returns the data directly to the caller.
     For FFI_SYSV the result is passed in r3/r4 if the struct size is less
     or equal 8 bytes.  */
  if (rtypenum == FFI_TYPE_STRUCT
      && !((cif->abi & FFI_SYSV_STRUCT_RET) != 0 && size <= 8))
    {
      rvalue = (void *) *pgr;
      ng++;
      pgr++;
    }

  i = 0;
  avn = cif->nargs;
  arg_types = cif->arg_types;

  /* Grab the addresses of the arguments from the stack frame.  */
  while (i < avn) {
    unsigned short typenum = arg_types[i]->type;

    /* We may need to handle some values depending on ABI.  */
    typenum = translate_float (cif->abi, typenum);

    switch (typenum)
      {
#ifndef __NO_FPRS__
      case FFI_TYPE_FLOAT:
	/* Unfortunately float values are stored as doubles
	   in the ffi_closure_SYSV code (since we don't check
	   the type in that routine).  */
	if (nf < NUM_FPR_ARG_REGISTERS)
	  {
	    /* FIXME? here we are really changing the values
	       stored in the original calling routines outgoing
	       parameter stack.  This is probably a really
	       naughty thing to do but...  */
	    double temp = pfr->d;
	    pfr->f = (float) temp;
	    avalue[i] = pfr;
	    nf++;
	    pfr++;
	  }
	else
	  {
	    avalue[i] = pst;
	    pst += 1;
	  }
	break;

      case FFI_TYPE_DOUBLE:
	if (nf < NUM_FPR_ARG_REGISTERS)
	  {
	    avalue[i] = pfr;
	    nf++;
	    pfr++;
	  }
	else
	  {
	    if (((long) pst) & 4)
	      pst++;
	    avalue[i] = pst;
	    pst += 2;
	  }
	break;

# if FFI_TYPE_LONGDOUBLE != FFI_TYPE_DOUBLE
      case FFI_TYPE_LONGDOUBLE:
	if (nf < NUM_FPR_ARG_REGISTERS - 1)
	  {
	    avalue[i] = pfr;
	    pfr += 2;
	    nf += 2;
	  }
	else
	  {
	    if (((long) pst) & 4)
	      pst++;
	    avalue[i] = pst;
	    pst += 4;
	    nf = 8;
	  }
	break;
# endif
#endif

      case FFI_TYPE_UINT128:
	/* Test if for the whole long double, 4 gprs are available.
	   otherwise the stuff ends up on the stack.  */
	if (ng < NUM_GPR_ARG_REGISTERS - 3)
	  {
	    avalue[i] = pgr;
	    pgr += 4;
	    ng += 4;
	  }
	else
	  {
	    avalue[i] = pst;
	    pst += 4;
	    ng = 8+4;
	  }
	break;

      case FFI_TYPE_SINT8:
      case FFI_TYPE_UINT8:
#ifndef __LITTLE_ENDIAN__
	if (ng < NUM_GPR_ARG_REGISTERS)
	  {
	    avalue[i] = (char *) pgr + 3;
	    ng++;
	    pgr++;
	  }
	else
	  {
	    avalue[i] = (char *) pst + 3;
	    pst++;
	  }
	break;
#endif

      case FFI_TYPE_SINT16:
      case FFI_TYPE_UINT16:
#ifndef __LITTLE_ENDIAN__
	if (ng < NUM_GPR_ARG_REGISTERS)
	  {
	    avalue[i] = (char *) pgr + 2;
	    ng++;
	    pgr++;
	  }
	else
	  {
	    avalue[i] = (char *) pst + 2;
	    pst++;
	  }
	break;
#endif

      case FFI_TYPE_SINT32:
      case FFI_TYPE_UINT32:
      case FFI_TYPE_POINTER:
	if (ng < NUM_GPR_ARG_REGISTERS)
	  {
	    avalue[i] = pgr;
	    ng++;
	    pgr++;
	  }
	else
	  {
	    avalue[i] = pst;
	    pst++;
	  }
	break;

      case FFI_TYPE_STRUCT:
	/* Structs are passed by reference. The address will appear in a
	   gpr if it is one of the first 8 arguments.  */
	if (ng < NUM_GPR_ARG_REGISTERS)
	  {
	    avalue[i] = (void *) *pgr;
	    ng++;
	    pgr++;
	  }
	else
	  {
	    avalue[i] = (void *) *pst;
	    pst++;
	  }
	break;

      case FFI_TYPE_SINT64:
      case FFI_TYPE_UINT64:
	/* Passing long long ints are complex, they must
	   be passed in suitable register pairs such as
	   (r3,r4) or (r5,r6) or (r6,r7), or (r7,r8) or (r9,r10)
	   and if the entire pair aren't available then the outgoing
	   parameter stack is used for both but an alignment of 8
	   must will be kept.  So we must either look in pgr
	   or pst to find the correct address for this type
	   of parameter.  */
	if (ng < NUM_GPR_ARG_REGISTERS - 1)
	  {
	    if (ng & 1)
	      {
		/* skip r4, r6, r8 as starting points */
		ng++;
		pgr++;
	      }
	    avalue[i] = pgr;
	    ng += 2;
	    pgr += 2;
	  }
	else
	  {
	    if (((long) pst) & 4)
	      pst++;
	    avalue[i] = pst;
	    pst += 2;
	    ng = NUM_GPR_ARG_REGISTERS;
	  }
	break;

      default:
	FFI_ASSERT (0);
      }

    i++;
  }

  (*fun) (cif, rvalue, avalue, user_data);

  /* Tell ffi_closure_SYSV how to perform return type promotions.
     Because the FFI_SYSV ABI returns the structures <= 8 bytes in
     r3/r4 we have to tell ffi_closure_SYSV how to treat them.  We
     combine the base type FFI_SYSV_TYPE_SMALL_STRUCT with the size of
     the struct less one.  We never have a struct with size zero.
     See the comment in ffitarget.h about ordering.  */
  if (rtypenum == FFI_TYPE_STRUCT
      && (cif->abi & FFI_SYSV_STRUCT_RET) != 0 && size <= 8)
    return FFI_SYSV_TYPE_SMALL_STRUCT - 1 + size;
  return rtypenum;
}
#endif