examples/non-const-visitor.cc

// Copyright 2014, ARM Limited
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#include "examples.h"
#include "non-const-visitor.h"

#define BUF_SIZE (4096)
#define __ masm->


void GenerateNonConstVisitorTestCode(MacroAssembler* masm) {
  // int64_t foo(int64_t a, int64_t b)
  //  Argument locations:
  //    a -> x0
  //    b -> x1
  __ Sub(x0, x0, x1);
  // The return value is in x0.
  __ Ret();
}


int64_t RunNonConstVisitorTestGeneratedCode(const Instruction* start_instr) {
#ifdef VIXL_INCLUDE_SIMULATOR
  Decoder simulator_decoder;
  Simulator simulator(&simulator_decoder);

  int64_t a = 5;
  int64_t b = 2;
  simulator.set_xreg(0, a);
  simulator.set_xreg(1, b);
  simulator.RunFrom(start_instr);
  int64_t res = simulator.xreg(0);
  printf("foo(%" PRId64 ", %" PRId64 ") = %" PRId64 "\n", a, b, res);

  return res;
#else
  // Without the simulator there is nothing to test.
  USE(start_instr);
  return 0;
#endif
}


#ifndef TEST_EXAMPLES
#ifdef VIXL_INCLUDE_SIMULATOR
int main(void) {
  // Create and initialize the assembler.
  byte assm_buf[BUF_SIZE];
  MacroAssembler masm(assm_buf, BUF_SIZE);

  // Generate the code.
  Label code_start, code_end;
  masm.Bind(&code_start);
  GenerateNonConstVisitorTestCode(&masm);
  masm.Bind(&code_end);
  masm.FinalizeCode();
  Instruction* instr_start = masm.GetLabelAddress<Instruction*>(&code_start);
  Instruction* instr_end = masm.GetLabelAddress<Instruction*>(&code_end);

  // Run the code a first time.
  RunNonConstVisitorTestGeneratedCode(instr_start);

  // Instantiate a decoder, disassembler, and our custom modifying visitor.
  Decoder decoder;
  PrintDisassembler disasm(stdout);
  SwitchAddSubRegisterSources modifying_visitor;

  // Register visitors in such a way that when visiting instructions, the
  // decoder will first disassemble the original instruction, modify it, and
  // then disassemble the modified instruction.
  decoder.AppendVisitor(&disasm);
  decoder.AppendVisitor(&modifying_visitor);
  decoder.AppendVisitor(&disasm);

  // Iterate through the instructions.
  Instruction* instr;
  for (instr = instr_start; instr < instr_end; instr += kInstructionSize) {
    printf("---\n");
    decoder.Decode(instr);
  }

  // Run the modified code and observe the different output from before.
  RunNonConstVisitorTestGeneratedCode(instr_start);

  return 0;
}
#else
// Without the simulator there is nothing to test.
int main(void) { return 0; }
#endif  // VIXL_INCLUDE_SIMULATOR
#endif  // TEST_EXAMPLES


// This is only used by the testing code.
void ModifyNonConstVisitorTestGeneratedCode(Instruction* start,
                                            Instruction* end) {
  Decoder decoder;
  SwitchAddSubRegisterSources modifying_visitor;
  decoder.AppendVisitor(&modifying_visitor);

  Instruction* instr;
  for (instr = start; instr < end; instr += kInstructionSize) {
    printf("---\n");
    decoder.Decode(instr);
  }
}