376 lines
7 KiB
C
376 lines
7 KiB
C
/* RETRO ------------------------------------------------------
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A personal, minimalistic forth
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Copyright (c) 2016 - 2019 Charles Childers
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---------------------------------------------------------- */
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#include <stdio.h>
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#include <stdint.h>
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#include <stdlib.h>
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#define CELL int32_t /* Cell size (32 bit, signed integer */
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#define IMAGE_SIZE 242000 /* Amount of RAM. 968kB by default. */
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#define ADDRESSES 256 /* Depth of address stack */
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#define STACK_DEPTH 128 /* Depth of data stack */
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CELL sp, rp, ip; /* Data, address, instruction pointers */
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CELL data[STACK_DEPTH]; /* The data stack */
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CELL address[ADDRESSES]; /* The address stack */
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CELL memory[IMAGE_SIZE + 1]; /* The memory for the image */
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#define TOS data[sp] /* Shortcut for top item on stack */
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#define NOS data[sp-1] /* Shortcut for second item on stack */
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#define TORS address[rp] /* Shortcut for top item on address stack */
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#define NUM_DEVICES 2
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typedef void (*Handler)(void);
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Handler IO_deviceHandlers[NUM_DEVICES + 1];
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Handler IO_queryHandlers[NUM_DEVICES + 1];
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#include "barebones_image.c"
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CELL stack_pop();
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void stack_push(CELL value);
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void execute(CELL cell);
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CELL ngaLoadImage();
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void ngaPrepare();
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void ngaProcessOpcode(CELL opcode);
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void ngaProcessPackedOpcodes(CELL opcode);
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int ngaValidatePackedOpcodes(CELL opcode);
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CELL stack_pop() {
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sp--;
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return data[sp + 1];
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}
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void stack_push(CELL value) {
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sp++;
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data[sp] = value;
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}
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void generic_output() {
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putc(stack_pop(), stdout);
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fflush(stdout);
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}
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void generic_output_query() {
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stack_push(0);
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stack_push(0);
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}
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void generic_input() {
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stack_push(getc(stdin));
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if (TOS == 127) TOS = 8;
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}
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void generic_input_query() {
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stack_push(0);
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stack_push(1);
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}
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void execute(CELL cell) {
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CELL opcode;
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rp = 1;
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ip = cell;
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while (ip < IMAGE_SIZE) {
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opcode = memory[ip];
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if (ngaValidatePackedOpcodes(opcode) != 0) {
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ngaProcessPackedOpcodes(opcode);
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} else {
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printf("Invalid instruction!\n");
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exit(1);
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}
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ip++;
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if (rp == 0)
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ip = IMAGE_SIZE;
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}
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}
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int main(int argc, char **argv) {
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IO_deviceHandlers[0] = generic_output;
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IO_deviceHandlers[1] = generic_input;
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IO_queryHandlers[0] = generic_output_query;
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IO_queryHandlers[1] = generic_input_query;
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ngaPrepare();
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ngaLoadImage();
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execute(0);
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exit(0);
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}
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/* Nga ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Copyright (c) 2008 - 2019, Charles Childers
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Copyright (c) 2009 - 2010, Luke Parrish
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Copyright (c) 2010, Marc Simpson
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Copyright (c) 2010, Jay Skeer
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Copyright (c) 2011, Kenneth Keating
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ */
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enum vm_opcode {
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VM_NOP, VM_LIT, VM_DUP, VM_DROP, VM_SWAP, VM_PUSH, VM_POP,
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VM_JUMP, VM_CALL, VM_CCALL, VM_RETURN, VM_EQ, VM_NEQ, VM_LT,
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VM_GT, VM_FETCH, VM_STORE, VM_ADD, VM_SUB, VM_MUL, VM_DIVMOD,
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VM_AND, VM_OR, VM_XOR, VM_SHIFT, VM_ZRET, VM_END, VM_IE,
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VM_IQ, VM_II
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};
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#define NUM_OPS VM_II + 1
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#ifndef NUM_DEVICES
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#define NUM_DEVICES 0
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#endif
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CELL ngaLoadImage(char *imageFile) {
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FILE *fp;
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CELL imageSize;
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long fileLen;
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CELL i;
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if ((fp = fopen(imageFile, "rb")) != NULL) {
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/* Determine length (in cells) */
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fseek(fp, 0, SEEK_END);
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fileLen = ftell(fp) / sizeof(CELL);
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rewind(fp);
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/* Read the file into memory */
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imageSize = fread(&memory, sizeof(CELL), fileLen, fp);
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fclose(fp);
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}
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else {
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for (i = 0; i < ngaImageCells; i++)
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memory[i] = ngaImage[i];
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imageSize = i;
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}
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return imageSize;
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}
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void ngaPrepare() {
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ip = sp = rp = 0;
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for (ip = 0; ip < IMAGE_SIZE; ip++)
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memory[ip] = VM_NOP;
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for (ip = 0; ip < STACK_DEPTH; ip++)
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data[ip] = 0;
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for (ip = 0; ip < ADDRESSES; ip++)
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address[ip] = 0;
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}
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void inst_nop() {
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}
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void inst_lit() {
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sp++;
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ip++;
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TOS = memory[ip];
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}
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void inst_dup() {
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sp++;
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data[sp] = NOS;
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}
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void inst_drop() {
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data[sp] = 0;
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if (--sp < 0)
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ip = IMAGE_SIZE;
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}
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void inst_swap() {
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CELL a;
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a = TOS;
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TOS = NOS;
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NOS = a;
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}
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void inst_push() {
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rp++;
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TORS = TOS;
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inst_drop();
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}
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void inst_pop() {
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sp++;
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TOS = TORS;
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rp--;
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}
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void inst_jump() {
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ip = TOS - 1;
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inst_drop();
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}
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void inst_call() {
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rp++;
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TORS = ip;
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ip = TOS - 1;
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inst_drop();
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}
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void inst_ccall() {
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CELL a, b;
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a = TOS; inst_drop(); /* False */
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b = TOS; inst_drop(); /* Flag */
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if (b != 0) {
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rp++;
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TORS = ip;
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ip = a - 1;
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}
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}
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void inst_return() {
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ip = TORS;
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rp--;
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}
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void inst_eq() {
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NOS = (NOS == TOS) ? -1 : 0;
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inst_drop();
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}
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void inst_neq() {
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NOS = (NOS != TOS) ? -1 : 0;
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inst_drop();
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}
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void inst_lt() {
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NOS = (NOS < TOS) ? -1 : 0;
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inst_drop();
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}
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void inst_gt() {
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NOS = (NOS > TOS) ? -1 : 0;
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inst_drop();
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}
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void inst_fetch() {
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switch (TOS) {
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case -1: TOS = sp - 1; break;
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case -2: TOS = rp; break;
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case -3: TOS = IMAGE_SIZE; break;
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default: TOS = memory[TOS]; break;
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}
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}
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void inst_store() {
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if (TOS <= IMAGE_SIZE && TOS >= 0) {
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memory[TOS] = NOS;
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inst_drop();
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inst_drop();
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} else {
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ip = IMAGE_SIZE;
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}
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}
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void inst_add() {
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NOS += TOS;
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inst_drop();
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}
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void inst_sub() {
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NOS -= TOS;
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inst_drop();
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}
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void inst_mul() {
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NOS *= TOS;
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inst_drop();
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}
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void inst_divmod() {
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CELL a, b;
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a = TOS;
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b = NOS;
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TOS = b / a;
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NOS = b % a;
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}
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void inst_and() {
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NOS = TOS & NOS;
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inst_drop();
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}
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void inst_or() {
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NOS = TOS | NOS;
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inst_drop();
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}
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void inst_xor() {
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NOS = TOS ^ NOS;
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inst_drop();
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}
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void inst_shift() {
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CELL y = TOS;
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CELL x = NOS;
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if (TOS < 0)
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NOS = NOS << (TOS * -1);
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else {
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if (x < 0 && y > 0)
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NOS = x >> y | ~(~0U >> y);
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else
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NOS = x >> y;
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}
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inst_drop();
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}
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void inst_zret() {
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if (TOS == 0) {
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inst_drop();
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ip = TORS;
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rp--;
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}
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}
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void inst_end() {
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ip = IMAGE_SIZE;
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}
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void inst_ie() {
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sp++;
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TOS = NUM_DEVICES;
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}
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void inst_iq() {
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CELL Device = TOS;
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inst_drop();
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IO_queryHandlers[Device]();
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}
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void inst_ii() {
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CELL Device = TOS;
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inst_drop();
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IO_deviceHandlers[Device]();
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}
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Handler instructions[NUM_OPS] = {
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inst_nop, inst_lit, inst_dup, inst_drop, inst_swap, inst_push, inst_pop,
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inst_jump, inst_call, inst_ccall, inst_return, inst_eq, inst_neq, inst_lt,
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inst_gt, inst_fetch, inst_store, inst_add, inst_sub, inst_mul, inst_divmod,
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inst_and, inst_or, inst_xor, inst_shift, inst_zret, inst_end, inst_ie,
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inst_iq, inst_ii
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};
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void ngaProcessOpcode(CELL opcode) {
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if (opcode != 0)
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instructions[opcode]();
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}
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int ngaValidatePackedOpcodes(CELL opcode) {
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CELL raw = opcode;
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CELL current;
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int valid = -1;
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int i;
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for (i = 0; i < 4; i++) {
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current = raw & 0xFF;
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if (!(current >= 0 && current <= 29))
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valid = 0;
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raw = raw >> 8;
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}
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return valid;
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}
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void ngaProcessPackedOpcodes(CELL opcode) {
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CELL raw = opcode;
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int i;
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for (i = 0; i < 4; i++) {
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ngaProcessOpcode(raw & 0xFF);
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raw = raw >> 8;
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}
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}
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