SLEIGH: How to Support Sin, Cos, and Sqrt?

I would like to close https://github.com/NationalSecurityAgency/ghidra/issues/1730. I believe I have disassembly for fsca and fsrra working. I have no clue to how to implement the pseudo code (http://www.shared-ptr.com/sh_insns.html):

fsca:

void FSCA (int n)
{
  if (FPSCR_PR != 0)
    undefined_operation ();
  else
  {
    float angle;
    long offset = 0x00010000;
    long fraction = 0x0000FFFF;

    set_I ();
    fraction &= FPUL;  // extract sub-rotation (fraction) part
    angle = fraction;  // convert to float
    angle = 2 * M_PI * angle / offset;  // convert to radian
    FR[n] = sin (angle);
    FR[n+1] = cos (angle);
    PC += 2;
  }
}

fsrra:

void FSRRA (int n)
{
  if (FPSCR_PR != 0)
    undefined_operation ();
  else
  {
    PC += 2;
    clear_cause();

    switch (data_type_of (n))
    {
    case NORM:
      if (sign_of (n) == 0)
      {
        set_I ();
        FR[n] = 1 / sqrt (FR[n]);
      }
      else
        invalid (n);
      break;

    case DENORM:
      if (sign_of (n) == 0)
        fpu_error ();
      else
        invalid (n);
      break;

    case PZERO:
    case NZERO:
      dz (n, sign_of (n));
      break;

    case PINF:
      FR[n] = 0;
      break;

    case NINF:
      invalid (n);
      break;

    case qNAN:
      qnan (n);
      break;

    case sNAN:
      invalid (n);
      break;
    }
  }
}

Any advice on how to tackle this? I found references in ia.sinc for pcodeops for cos. I don’t quite understand it. Thanks in advance.

[nneonneo]

You could implement it as a pcodeop, which is effectively just an opaque “intrinsic” operation. It gets decompiled as simply a function call.

Declare the pcodeop somewhere in your slaspec as

define pcodeop sin;

Then in your constructor just do

r0 = sin(r0);

The “functions” thus declared by pcodeop can take any arguments and return anything.

See section “7.7.1.8. User-Defined Operations” in the SLEIGH manual, which says the following:

7.7.1.8. User-Defined Operations

Any identifier that has been defined as a new p-code operation, using the define pcodeop statement, can be invoked as an operator using functional syntax. The SLEIGH compiler assumes that the operator can take an arbitrary number of inputs, and if used in an expression, the compiler assumes the operation returns an output. Using this syntax of course generates the particular p-code operation reserved for the identifier.

define pcodeop arctan; ... :atan r1,r2 is opcode=0xa3 & r1 & r2 { r1 = arctan(r2); }

[GhidorahRex]

You also need to take care with how you handle the Fr[N+1] for the cos.

Your best bet here would be to add an additional token and attach statement: FRN_1 = (8,11) ... attach variables [FRN_1] [fr1 fr2 fr3 fr4 fr5 fr6 fr7 fr8 fr9 fr10 fr11 fr12 fr13 fr14 fr15 _ ]; FRN_1t: FRN_1 is FRN_1 { export FRN_1; } :fsca fpul_t, FRN_0t is fpul_t & FRN_0t & FRN_1t ...