/***************************************************************
   crc's _ _
        (_) | ___
        | | |/ _ \  a tiny virtual computer
        | | | (_) | 64kw RAM, 32-bit, Dual Stack, MISC
        |_|_|\___/  ilo.c (c) charles childers

 ilo-fast.c modifications (c) 2024 Christopher Leonard

 Recommended compiler flags:

   -O3 -fomit-frame-pointer -funroll-loops
   -march=native -ftree-vectorize

 **************************************************************/

#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>

#define T ds[sp]    /* Top of Data Stack    */
#define N ds[sp-1]  /* Next on Data Stack   */
#define R as[rp]    /* Top of Address Stack */
#define V static void
#define I int
#define C char

static C *blocks,   /* name of block file (ilo.blocks) */
         *rom;      /* name of image (ilo.rom)         */

#define push(v) { ds[sp + 1] = (v); sp += 1; }
#define pop() ( sp -= 1, ds[sp + 1] )

#define load_image() { \
  f = open(rom, O_RDONLY, 0666); \
  if (!f) { return; }; \
  read(f, &m, 65536 * 4); \
  close(f); \
  ip = sp = rp = 0; \
}

#define save_image() { \
  f = open(rom, O_WRONLY, 0666); \
  write(f, &m, 65536 * 4); \
  close(f); \
}

#define block_common() { \
  b = pop(); /* block buffer */ \
  a = pop(); /* block number */ \
  lseek(f, 4096 * a, SEEK_SET); \
}

#define read_block() { \
  f = open(blocks, O_RDONLY, 0666); \
  block_common(); \
  read(f, m + b, 4096); \
  close(f); \
}

#define write_block() { \
  f = open(blocks, O_WRONLY, 0666); \
  block_common(); \
  write(f, m + b, 4096); \
  close(f); \
}

#define save_ip() { rp += 1; R = ip; }
#define symmetric() { if (b >= 0 && N < 0) { T += 1; N -= b; } }

#define li() { ip += 1; push(m[ip]); }
#define du() { push(T); }
#define dr() { ds[sp] = 0; sp -= 1; }
#define sw() { a = T; T = N; N = a; }
#define pu() { rp += 1; R = pop(); }
#define po() { push(R); rp -= 1; }
#define ju() { ip = pop() - 1; }
#define ca() { save_ip(); ip = pop() - 1; }
#define cc() { a = pop(); if (pop()) { save_ip(); ip = a - 1; } }
#define cj() { a = pop(); if (pop()) { ip = a - 1; } }
#define re() { ip = R; rp -= 1; }
#define eq() { N = (N == T) ? -1 : 0; sp -= 1; }
#define ne() { N = (N != T) ? -1 : 0; sp -= 1; }
#define lt() { N = (N <  T) ? -1 : 0; sp -= 1; }
#define gt() { N = (N >  T) ? -1 : 0; sp -= 1; }
#define fe() { T = m[T]; }
#define st() { m[T] = N; sp -= 2; }
#define ad() { N += T; sp -= 1; }
#define su() { N -= T; sp -= 1; }
#define mu() { N *= T; sp -= 1; }
#define di() { a = T; b = N; T = b / a; N = b % a; symmetric(); }
#define an() { N = T & N; sp -= 1; }
#define or() { N = T | N; sp -= 1; }
#define xo() { N = T ^ N; sp -= 1; }
#define sl() { N = N << T; sp -= 1; }
#define sr() { N = N >> T; sp -= 1; }
#define cp() { l = pop(); d = pop(); s = T; T = -1; \
         while (l) { if (m[d] != m[s]) { T = 0; } \
                     l -= 1; s += 1; d += 1; } }
#define cy() { l = pop(); d = pop(); s = pop(); \
         while (l) { m[d] = m[s]; l -= 1; s += 1; d += 1; } }
#define ioa() { i[0] = (char)pop(); write(1, &i, 1); }
#define iob() { read(0, &i, 1); push(i[0]); }
#define ioc() { read_block(); }
#define iod() { write_block(); }
#define ioe() { save_image(); }
#define iof() { load_image(); ip = -1; }
#define iog() { ip = 65536; }
#define ioh() { push(sp); push(rp); }
#define io() { \
  switch (pop()) { \
    case 0: ioa(); break;  case 1: iob(); break; \
    case 2: ioc(); break;  case 3: iod(); break; \
    case 4: ioe(); break;  case 5: iof(); break; \
    case 6: iog(); break;  case 7: ioh(); break; \
    default: break; \
  } \
}

/* Using a switch here instead of a jump table to avoid   */
/* some issues w/relocation stuff when building w/o libc  */

V execute() {

I ip,        /* instruction pointer             */
  sp,        /* data stack pointer              */
  rp,        /* address stack pointer           */
  ds[33],    /* data stack                      */
  as[257],   /* address stack                   */
  m[65536];  /* memory                          */

/* the other variables are used by the various
   functions for misc. purposes                   */

I a, b, f, s, d, l;
C i[1];
  load_image();
  for (; ip < 65536; ip++) {
    I opcode = m[ip];
    I bundle;
    for (bundle = 0; bundle < 4; bundle++) {
      I o = (opcode >> (8*bundle)) & 0xFF;
      switch (o) {
        case  0:       break;   case  1: li(); break;
        case  2: du(); break;   case  3: dr(); break;
        case  4: sw(); break;   case  5: pu(); break;
        case  6: po(); break;   case  7: ju(); break;
        case  8: ca(); break;   case  9: cc(); break;
        case 10: cj(); break;   case 11: re(); break;
        case 12: eq(); break;   case 13: ne(); break;
        case 14: lt(); break;   case 15: gt(); break;
        case 16: fe(); break;   case 17: st(); break;
        case 18: ad(); break;   case 19: su(); break;
        case 20: mu(); break;   case 21: di(); break;
        case 22: an(); break;   case 23: or(); break;
        case 24: xo(); break;   case 25: sl(); break;
        case 26: sr(); break;   case 27: cp(); break;
        case 28: cy(); break;   case 29: io(); break;
        default: break;
      }
    }
  }
#if 0
#ifndef NOSTDLIB
  for (; sp > 0; sp -= 1) printf(" %d", ds[sp]); printf("\n");
#endif
#endif
}

I main(I argc, C **argv) {
#ifndef NOSTDLIB
  blocks = (argc > 1) ? argv[1] : "ilo.blocks";
  rom    = (argc > 2) ? argv[2] : "ilo.rom";
#else
  blocks = "ilo.blocks";
  rom = "ilo.rom";
#endif
  execute();
  return 0;
}