freedreno/afuc/disasm.c

/*
 * Copyright (c) 2017 Rob Clark <robdclark@gmail.com>
 *
 * 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 (including the next
 * paragraph) 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 AUTHORS OR COPYRIGHT HOLDERS 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 <assert.h>
#include <err.h>
#include <fcntl.h>
#include <getopt.h>
#include <stdarg.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "util/os_file.h"

#include "freedreno_pm4.h"

#include "afuc.h"
#include "util.h"
#include "emu.h"

static int gpuver;

/* non-verbose mode should output something suitable to feed back into
 * assembler.. verbose mode has additional output useful for debugging
 * (like unexpected bits that are set)
 */
static bool verbose = false;

/* emulator mode: */
static bool emulator = false;

static void
print_gpu_reg(uint32_t regbase)
{
   if (regbase < 0x100)
      return;

   char *name = afuc_gpu_reg_name(regbase);
   if (name) {
      printf("\t; %s", name);
      free(name);
   }
}

#define printerr(fmt, ...) afuc_printc(AFUC_ERR, fmt, ##__VA_ARGS__)
#define printlbl(fmt, ...) afuc_printc(AFUC_LBL, fmt, ##__VA_ARGS__)

void
print_src(unsigned reg)
{
   if (reg == REG_REM)
      printf("$rem"); /* remainding dwords in packet */
   else if (reg == REG_MEMDATA)
      printf("$memdata");
   else if (reg == REG_REGDATA)
      printf("$regdata");
   else if (reg == REG_DATA)
      printf("$data");
   else
      printf("$%02x", reg);
}

void
print_dst(unsigned reg)
{
   if (reg == REG_REM)
      printf("$rem"); /* remainding dwords in packet */
   else if (reg == REG_ADDR)
      printf("$addr");
   else if (reg == REG_USRADDR)
      printf("$usraddr");
   else if (reg == REG_DATA)
      printf("$data");
   else
      printf("$%02x", reg);
}

static void
print_alu_name(afuc_opc opc, uint32_t instr)
{
   if (opc == OPC_ADD) {
      printf("add ");
   } else if (opc == OPC_ADDHI) {
      printf("addhi ");
   } else if (opc == OPC_SUB) {
      printf("sub ");
   } else if (opc == OPC_SUBHI) {
      printf("subhi ");
   } else if (opc == OPC_AND) {
      printf("and ");
   } else if (opc == OPC_OR) {
      printf("or ");
   } else if (opc == OPC_XOR) {
      printf("xor ");
   } else if (opc == OPC_NOT) {
      printf("not ");
   } else if (opc == OPC_SHL) {
      printf("shl ");
   } else if (opc == OPC_USHR) {
      printf("ushr ");
   } else if (opc == OPC_ISHR) {
      printf("ishr ");
   } else if (opc == OPC_ROT) {
      printf("rot ");
   } else if (opc == OPC_MUL8) {
      printf("mul8 ");
   } else if (opc == OPC_MIN) {
      printf("min ");
   } else if (opc == OPC_MAX) {
      printf("max ");
   } else if (opc == OPC_CMP) {
      printf("cmp ");
   } else if (opc == OPC_MSB) {
      printf("msb ");
   } else {
      printerr("[%08x]", instr);
      printf("  ; alu%02x ", opc);
   }
}

static const char *
getpm4(uint32_t id)
{
   return afuc_pm_id_name(id);
}

static struct {
   uint32_t offset;
   uint32_t num_jump_labels;
   uint32_t jump_labels[256];
} jump_labels[1024];
int num_jump_labels;

static void
add_jump_table_entry(uint32_t n, uint32_t offset)
{
   int i;

   if (n > 128) /* can't possibly be a PM4 PKT3.. */
      return;

   for (i = 0; i < num_jump_labels; i++)
      if (jump_labels[i].offset == offset)
         goto add_label;

   num_jump_labels = i + 1;
   jump_labels[i].offset = offset;
   jump_labels[i].num_jump_labels = 0;

add_label:
   jump_labels[i].jump_labels[jump_labels[i].num_jump_labels++] = n;
   assert(jump_labels[i].num_jump_labels < 256);
}

static int
get_jump_table_entry(uint32_t offset)
{
   int i;

   for (i = 0; i < num_jump_labels; i++)
      if (jump_labels[i].offset == offset)
         return i;

   return -1;
}

static uint32_t label_offsets[0x512];
static int num_label_offsets;

static int
label_idx(uint32_t offset, bool create)
{
   int i;
   for (i = 0; i < num_label_offsets; i++)
      if (offset == label_offsets[i])
         return i;
   if (!create)
      return -1;
   label_offsets[i] = offset;
   num_label_offsets = i + 1;
   return i;
}

static const char *
label_name(uint32_t offset, bool allow_jt)
{
   static char name[12];
   int lidx;

   if (allow_jt) {
      lidx = get_jump_table_entry(offset);
      if (lidx >= 0) {
         int j;
         for (j = 0; j < jump_labels[lidx].num_jump_labels; j++) {
            uint32_t jump_label = jump_labels[lidx].jump_labels[j];
            const char *str = getpm4(jump_label);
            if (str)
               return str;
         }
         // if we don't find anything w/ known name, maybe we should
         // return UNKN%d to at least make it clear that this is some
         // sort of jump-table entry?
      }
   }

   lidx = label_idx(offset, false);
   if (lidx < 0)
      return NULL;
   sprintf(name, "l%03d", lidx);
   return name;
}

static uint32_t fxn_offsets[0x512];
static int num_fxn_offsets;

static int
fxn_idx(uint32_t offset, bool create)
{
   int i;
   for (i = 0; i < num_fxn_offsets; i++)
      if (offset == fxn_offsets[i])
         return i;
   if (!create)
      return -1;
   fxn_offsets[i] = offset;
   num_fxn_offsets = i + 1;
   return i;
}

static const char *
fxn_name(uint32_t offset)
{
   static char name[14];
   int fidx = fxn_idx(offset, false);
   if (fidx < 0)
      return NULL;
   sprintf(name, "fxn%02d", fidx);
   return name;
}

void
print_control_reg(uint32_t id)
{
   char *name = afuc_control_reg_name(id);
   if (name) {
      printf("@%s", name);
      free(name);
   } else {
      printf("0x%03x", id);
   }
}

void
print_pipe_reg(uint32_t id)
{
   char *name = afuc_pipe_reg_name(id);
   if (name) {
      printf("|%s", name);
      free(name);
   } else {
      printf("0x%03x", id);
   }
}

static void
disasm_instr(uint32_t *instrs, unsigned pc)
{
   int jump_label_idx;
   afuc_instr *instr = (void *)&instrs[pc];
   const char *fname, *lname;
   afuc_opc opc;
   bool rep;

   afuc_get_opc(instr, &opc, &rep);

   lname = label_name(pc, false);
   fname = fxn_name(pc);
   jump_label_idx = get_jump_table_entry(pc);

   if (jump_label_idx >= 0) {
      int j;
      printf("\n");
      for (j = 0; j < jump_labels[jump_label_idx].num_jump_labels; j++) {
         uint32_t jump_label = jump_labels[jump_label_idx].jump_labels[j];
         const char *name = getpm4(jump_label);
         if (name) {
            printlbl("%s", name);
         } else {
            printlbl("UNKN%d", jump_label);
         }
         printf(":\n");
      }
   }

   if (fname) {
      printlbl("%s", fname);
      printf(":\n");
   }

   if (lname) {
      printlbl(" %s", lname);
      printf(":");
   } else {
      printf("      ");
   }

   if (verbose) {
      printf("\t%04x: %08x  ", pc, instrs[pc]);
   } else {
      printf("  ");
   }

   switch (opc) {
   case OPC_NOP: {
      /* a6xx changed the default immediate, and apparently 0
       * is illegal now.
       */
      const uint32_t nop = gpuver >= 6 ? 0x1000000 : 0x0;
      if (instrs[pc] != nop) {
         printerr("[%08x]", instrs[pc]);
         printf("  ; ");
      }
      if (rep)
         printf("(rep)");
      printf("nop");
      print_gpu_reg(instrs[pc]);

      break;
   }
   case OPC_ADD:
   case OPC_ADDHI:
   case OPC_SUB:
   case OPC_SUBHI:
   case OPC_AND:
   case OPC_OR:
   case OPC_XOR:
   case OPC_NOT:
   case OPC_SHL:
   case OPC_USHR:
   case OPC_ISHR:
   case OPC_ROT:
   case OPC_MUL8:
   case OPC_MIN:
   case OPC_MAX:
   case OPC_CMP: {
      bool src1 = true;

      if (opc == OPC_NOT)
         src1 = false;

      if (rep)
         printf("(rep)");

      print_alu_name(opc, instrs[pc]);
      print_dst(instr->alui.dst);
      printf(", ");
      if (src1) {
         print_src(instr->alui.src);
         printf(", ");
      }
      printf("0x%04x", instr->alui.uimm);
      print_gpu_reg(instr->alui.uimm);

      /* print out unexpected bits: */
      if (verbose) {
         if (instr->alui.src && !src1)
            printerr("  (src=%02x)", instr->alui.src);
      }

      break;
   }
   case OPC_MOVI: {
      if (rep)
         printf("(rep)");
      printf("mov ");
      print_dst(instr->movi.dst);
      printf(", 0x%04x", instr->movi.uimm);
      if (instr->movi.shift)
         printf(" << %u", instr->movi.shift);

      if ((instr->movi.dst == REG_ADDR) && (instr->movi.shift >= 16)) {
         uint32_t val = (uint32_t)instr->movi.uimm << (uint32_t)instr->movi.shift;
         val &= ~0x40000;  /* b18 seems to be a flag */

         if ((val & 0x00ffffff) == 0) {
            printf("\t; ");
            print_pipe_reg(val >> 24);
            break;
         }
      }
      /* using mov w/ << 16 is popular way to construct a pkt7
       * header to send (for ex, from PFP to ME), so check that
       * case first
       */
      if ((instr->movi.shift == 16) &&
          ((instr->movi.uimm & 0xff00) == 0x7000)) {
         unsigned opc, p;

         opc = instr->movi.uimm & 0x7f;
         p = pm4_odd_parity_bit(opc);

         /* So, you'd think that checking the parity bit would be
          * a good way to rule out false positives, but seems like
          * ME doesn't really care.. at least it would filter out
          * things that look like actual legit packets between
          * PFP and ME..
          */
         if (1 || p == ((instr->movi.uimm >> 7) & 0x1)) {
            const char *name = getpm4(opc);
            printf("\t; ");
            if (name)
               printlbl("%s", name);
            else
               printlbl("UNKN%u", opc);
            break;
         }
      }

      print_gpu_reg((uint32_t)instr->movi.uimm << (uint32_t)instr->movi.shift);

      break;
   }
   case OPC_ALU: {
      bool src1 = true;

      if (instr->alu.alu == OPC_NOT || instr->alu.alu == OPC_MSB)
         src1 = false;

      if (instr->alu.pad)
         printf("[%08x]  ; ", instrs[pc]);

      if (rep)
         printf("(rep)");
      if (instr->alu.xmov)
         printf("(xmov%d)", instr->alu.xmov);

      /* special case mnemonics:
       *   reading $00 seems to always yield zero, and so:
       *      or $dst, $00, $src -> mov $dst, $src
       *   Maybe add one for negate too, ie.
       *      sub $dst, $00, $src ???
       */
      if ((instr->alu.alu == OPC_OR) && !instr->alu.src1) {
         printf("mov ");
         src1 = false;
      } else {
         print_alu_name(instr->alu.alu, instrs[pc]);
      }

      print_dst(instr->alu.dst);
      if (src1) {
         printf(", ");
         print_src(instr->alu.src1);
      }
      printf(", ");
      print_src(instr->alu.src2);

      /* print out unexpected bits: */
      if (verbose) {
         if (instr->alu.pad)
            printerr("  (pad=%01x)", instr->alu.pad);
         if (instr->alu.src1 && !src1)
            printerr("  (src1=%02x)", instr->alu.src1);
      }

      /* xmov is a modifier that makes the processor execute up to 3
       * extra mov's after the current instruction. Given an ALU
       * instruction:
       *
       * (xmovN) alu $dst, $src1, $src2
       *
       * In all of the uses in the firmware blob, $dst and $src2 are one
       * of the "special" registers $data, $addr, $addr2. I've observed
       * that if $dst isn't "special" then it's replaced with $00
       * instead of $data, but I haven't checked what happens if $src2
       * isn't "special".  Anyway, in the usual case, the HW produces a
       * count M = min(N, $rem) and then does the following:
       *
       * M = 1:
       * mov $data, $src2
       *
       * M = 2:
       * mov $data, $src2
       * mov $data, $src2
       *
       * M = 3:
       * mov $data, $src2
       * mov $dst, $src2 (special case for CP_CONTEXT_REG_BUNCH)
       * mov $data, $src2
       *
       * It seems to be frequently used in combination with (rep) to
       * provide a kind of hardware-based loop unrolling, and there's
       * even a special case in the ISA to be able to do this with
       * CP_CONTEXT_REG_BUNCH. However (rep) isn't required.
       *
       * This dumps the expected extra instructions, assuming that $rem
       * isn't too small.
       */
      if (verbose && instr->alu.xmov) {
         for (int i = 0; i < instr->alu.xmov; i++) {
            printf("\n        ; mov ");
            if (instr->alu.dst < 0x1d)
               printf("$00");
            else if (instr->alu.xmov == 3 && i == 1)
               print_dst(instr->alu.dst);
            else
               printf("$data");
            printf(", ");
            print_src(instr->alu.src2);
         }
      }

      break;
   }
   case OPC_CWRITE6:
   case OPC_CREAD6:
   case OPC_STORE6:
   case OPC_LOAD6: {
      if (rep)
         printf("(rep)");

      bool is_control_reg = true;
      bool is_store = true;
      if (gpuver >= 6) {
         switch (opc) {
         case OPC_CWRITE6:
            printf("cwrite ");
            break;
         case OPC_CREAD6:
            is_store = false;
            printf("cread ");
            break;
         case OPC_STORE6:
            is_control_reg = false;
            printf("store ");
            break;
         case OPC_LOAD6:
            is_control_reg = false;
            is_store = false;
            printf("load ");
            break;
         default:
            assert(!"unreachable");
         }
      } else {
         switch (opc) {
         case OPC_CWRITE5:
            printf("cwrite ");
            break;
         case OPC_CREAD5:
            is_store = false;
            printf("cread ");
            break;
         default:
            fprintf(stderr, "A6xx control opcode on A5xx?\n");
            exit(1);
         }
      }

      if (is_store)
         print_src(instr->control.src1);
      else
         print_dst(instr->control.src1);
      printf(", [");
      print_src(instr->control.src2);
      printf(" + ");
      if (is_control_reg && instr->control.flags != 0x4)
         print_control_reg(instr->control.uimm);
      else
         printf("0x%03x", instr->control.uimm);
      printf("], 0x%x", instr->control.flags);
      break;
   }
   case OPC_BRNEI:
   case OPC_BREQI:
   case OPC_BRNEB:
   case OPC_BREQB: {
      unsigned off = pc + instr->br.ioff;

      assert(!rep);

      /* Since $00 reads back zero, it can be used as src for
       * unconditional branches.  (This only really makes sense
       * for the BREQB.. or possible BRNEI if imm==0.)
       *
       * If bit=0 then branch is taken if *all* bits are zero.
       * Otherwise it is taken if bit (bit-1) is clear.
       *
       * Note the instruction after a jump/branch is executed
       * regardless of whether branch is taken, so use nop or
       * take that into account in code.
       */
      if (instr->br.src || (opc != OPC_BRNEB)) {
         bool immed = false;

         if (opc == OPC_BRNEI) {
            printf("brne ");
            immed = true;
         } else if (opc == OPC_BREQI) {
            printf("breq ");
            immed = true;
         } else if (opc == OPC_BRNEB) {
            printf("brne ");
         } else if (opc == OPC_BREQB) {
            printf("breq ");
         }
         print_src(instr->br.src);
         if (immed) {
            printf(", 0x%x,", instr->br.bit_or_imm);
         } else {
            printf(", b%u,", instr->br.bit_or_imm);
         }
      } else {
         printf("jump");
         if (verbose && instr->br.bit_or_imm) {
            printerr("  (src=%03x, bit=%03x) ", instr->br.src,
                     instr->br.bit_or_imm);
         }
      }

      printf(" #");
      printlbl("%s", label_name(off, true));
      if (verbose)
         printf(" (#%d, %04x)", instr->br.ioff, off);
      break;
   }
   case OPC_CALL:
      assert(!rep);
      printf("call #");
      printlbl("%s", fxn_name(instr->call.uoff));
      if (verbose) {
         printf(" (%04x)", instr->call.uoff);
         if (instr->br.bit_or_imm || instr->br.src) {
            printerr("  (src=%03x, bit=%03x) ", instr->br.src,
                     instr->br.bit_or_imm);
         }
      }
      break;
   case OPC_RET:
      assert(!rep);
      if (instr->ret.pad)
         printf("[%08x]  ; ", instrs[pc]);
      if (instr->ret.interrupt)
         printf("iret");
      else
         printf("ret");
      break;
   case OPC_WIN:
      assert(!rep);
      if (instr->waitin.pad)
         printf("[%08x]  ; ", instrs[pc]);
      printf("waitin");
      if (verbose && instr->waitin.pad)
         printerr("  (pad=%x)", instr->waitin.pad);
      break;
   case OPC_PREEMPTLEAVE6:
      if (gpuver < 6) {
         printf("[%08x]  ; op38", instrs[pc]);
      } else {
         printf("preemptleave #");
         printlbl("%s", label_name(instr->call.uoff, true));
      }
      break;
   case OPC_SETSECURE:
      /* Note: This seems to implicitly read the secure/not-secure state
       * to set from the low bit of $02, and implicitly jumps to pc + 3
       * (i.e. skipping the next two instructions) if it succeeds. We
       * print these implicit parameters to make reading the disassembly
       * easier.
       */
      if (instr->pad)
         printf("[%08x]  ; ", instrs[pc]);
      printf("setsecure $02, #");
      printlbl("%s", label_name(pc + 3, true));
      break;
   default:
      printerr("[%08x]", instrs[pc]);
      printf("  ; op%02x ", opc);
      print_dst(instr->alui.dst);
      printf(", ");
      print_src(instr->alui.src);
      print_gpu_reg(instrs[pc] & 0xffff);
      break;
   }
   printf("\n");
}

static void
setup_packet_table(uint32_t *jmptbl, uint32_t sizedwords)
{
   num_jump_labels = 0;

   for (unsigned i = 0; i < sizedwords; i++) {
      unsigned offset = jmptbl[i];
      unsigned n = i; // + CP_NOP;
      add_jump_table_entry(n, offset);
   }
}

static void
setup_labels(uint32_t *instrs, uint32_t sizedwords)
{
   afuc_opc opc;
   bool rep;

   num_label_offsets = 0;

   for (unsigned i = 0; i < sizedwords; i++) {
      afuc_instr *instr = (void *)&instrs[i];

      afuc_get_opc(instr, &opc, &rep);

      switch (opc) {
      case OPC_BRNEI:
      case OPC_BREQI:
      case OPC_BRNEB:
      case OPC_BREQB:
         label_idx(i + instr->br.ioff, true);
         break;
      case OPC_PREEMPTLEAVE6:
         if (gpuver >= 6)
            label_idx(instr->call.uoff, true);
         break;
      case OPC_CALL:
         fxn_idx(instr->call.uoff, true);
         break;
      case OPC_SETSECURE:
         /* this implicitly jumps to pc + 3 if successful */
         label_idx(i + 3, true);
         break;
      default:
         break;
      }
   }
}

static void
disasm(struct emu *emu)
{
   uint32_t sizedwords = emu->sizedwords;
   uint32_t lpac_offset = 0;

   EMU_GPU_REG(CP_SQE_INSTR_BASE);
   EMU_GPU_REG(CP_LPAC_SQE_INSTR_BASE);

   emu_init(emu);

#ifdef BOOTSTRAP_DEBUG
   while (true) {
      disasm_instr(emu->instrs, emu->gpr_regs.pc);
      emu_step(emu);
   }
#endif

   emu_run_bootstrap(emu);

   /* Figure out if we have LPAC SQE appended: */
   if (emu_get_reg64(emu, &CP_LPAC_SQE_INSTR_BASE)) {
      lpac_offset = emu_get_reg64(emu, &CP_LPAC_SQE_INSTR_BASE) -
            emu_get_reg64(emu, &CP_SQE_INSTR_BASE);
      lpac_offset /= 4;
      sizedwords = lpac_offset;
   }

   setup_packet_table(emu->jmptbl, ARRAY_SIZE(emu->jmptbl));
   setup_labels(emu->instrs, emu->sizedwords);

   /* TODO add option to emulate LPAC SQE instead: */
   if (emulator) {
      /* Start from clean slate: */
      emu_fini(emu);
      emu_init(emu);

      while (true) {
         disasm_instr(emu->instrs, emu->gpr_regs.pc);
         emu_step(emu);
      }
   }

   /* print instructions: */
   for (int i = 0; i < sizedwords; i++) {
      disasm_instr(emu->instrs, i);
   }

   if (!lpac_offset)
      return;

   printf(";\n");
   printf("; LPAC microcode:\n");
   printf(";\n");

   emu_fini(emu);

   emu->lpac = true;
   emu->instrs += lpac_offset;
   emu->sizedwords -= lpac_offset;

   emu_init(emu);
   emu_run_bootstrap(emu);

   setup_packet_table(emu->jmptbl, ARRAY_SIZE(emu->jmptbl));
   setup_labels(emu->instrs, emu->sizedwords);

   /* print instructions: */
   for (int i = 0; i < emu->sizedwords; i++) {
      disasm_instr(emu->instrs, i);
   }
}


static void
disasm_legacy(uint32_t *buf, int sizedwords)
{
   uint32_t *instrs = buf;
   const int jmptbl_start = instrs[1] & 0xffff;
   uint32_t *jmptbl = &buf[jmptbl_start];
   int i;

   /* parse jumptable: */
   setup_packet_table(jmptbl, 0x80);

   /* do a pre-pass to find instructions that are potential branch targets,
    * and add labels for them:
    */
   setup_labels(instrs, jmptbl_start);

   /* print instructions: */
   for (i = 0; i < jmptbl_start; i++) {
      disasm_instr(instrs, i);
   }

   /* print jumptable: */
   if (verbose) {
      printf(";;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;\n");
      printf("; JUMP TABLE\n");
      for (i = 0; i < 0x7f; i++) {
         int n = i; // + CP_NOP;
         uint32_t offset = jmptbl[i];
         const char *name = getpm4(n);
         printf("%3d %02x: ", n, n);
         printf("%04x", offset);
         if (name) {
            printf("   ; %s", name);
         } else {
            printf("   ; UNKN%d", n);
         }
         printf("\n");
      }
   }
}

static void
usage(void)
{
   fprintf(stderr, "Usage:\n"
                   "\tdisasm [-g GPUVER] [-v] [-c] filename.asm\n"
                   "\t\t-g - specify GPU version (5, etc)\n"
                   "\t\t-c - use colors\n"
                   "\t\t-v - verbose output\n"
                   "\t\t-e - emulator mode\n");
   exit(2);
}

int
main(int argc, char **argv)
{
   uint32_t *buf;
   char *file;
   bool colors = false;
   uint32_t gpu_id = 0;
   size_t sz;
   int c, ret;
   bool unit_test = false;

   /* Argument parsing: */
   while ((c = getopt(argc, argv, "g:vceu")) != -1) {
      switch (c) {
      case 'g':
         gpu_id = atoi(optarg);
         break;
      case 'v':
         verbose = true;
         break;
      case 'c':
         colors = true;
         break;
      case 'e':
         emulator = true;
         verbose  = true;
         break;
      case 'u':
         unit_test = true;
         break;
      default:
         usage();
      }
   }

   if (optind >= argc) {
      fprintf(stderr, "no file specified!\n");
      usage();
   }

   file = argv[optind];

   /* if gpu version not specified, infer from filename: */
   if (!gpu_id) {
      char *str = strstr(file, "a5");
      if (!str)
         str = strstr(file, "a6");
      if (str)
         gpu_id = atoi(str + 1);
   }

   if (gpu_id < 500) {
      printf("invalid gpu_id: %d\n", gpu_id);
      return -1;
   }

   gpuver = gpu_id / 100;

   /* a6xx is *mostly* a superset of a5xx, but some opcodes shuffle
    * around, and behavior of special regs is a bit different.  Right
    * now we only bother to support the a6xx variant.
    */
   if (emulator && (gpuver != 6)) {
      fprintf(stderr, "Emulator only supported on a6xx!\n");
      return 1;
   }

   ret = afuc_util_init(gpuver, colors);
   if (ret < 0) {
      usage();
   }

   printf("; a%dxx microcode\n", gpuver);

   buf = (uint32_t *)os_read_file(file, &sz);

   if (!unit_test)
      printf("; Disassembling microcode: %s\n", file);
   printf("; Version: %08x\n\n", buf[1]);

   if (gpuver < 6) {
      disasm_legacy(&buf[1], sz / 4 - 1);
   } else {
      struct emu emu = {
            .instrs = &buf[1],
            .sizedwords = sz / 4 - 1,
            .gpu_id = gpu_id,
      };

      disasm(&emu);
   }

   return 0;
}