benchmarks/bench-branch.cc

// Copyright 2015, ARM Limited
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#include "vixl/a64/macro-assembler-a64.h"
#include "vixl/a64/instructions-a64.h"
#include "vixl/globals.h"

using namespace vixl;

static const int kDefaultInstructionCount = 100000;

// This program focuses on emitting branch instructions.
//
// This code will emit a given number of branch immediate to the next
// instructions in a fixed size buffer, looping over the buffer if necessary.
// This code therefore focuses on Emit and label binding/patching.
int main(int argc, char* argv[]) {
  int instructions = 0;

  switch (argc) {
    case 1:
      instructions = kDefaultInstructionCount;
      break;
    case 2:
      instructions = atoi(argv[1]);
      break;
    default:
      printf("Usage: %s [#instructions]\n", argv[0]);
      exit(1);
  }

  const int buffer_size = 256 * KBytes;
  const int buffer_instruction_count = buffer_size / kInstructionSize;
  MacroAssembler masm(buffer_size);

#define __ masm.
  // We emit a branch to the next instruction.

  int rounds = instructions / buffer_instruction_count;
  for (int i = 0; i < rounds; ++i) {
    {
      InstructionAccurateScope scope(&masm, buffer_instruction_count);
      for (int j = 0; j < buffer_instruction_count; ++j) {
        Label target;
        __ b(&target);
        __ bind(&target);
      }
    }
    masm.Reset();
  }

  int remaining = instructions % buffer_instruction_count;
  {
    InstructionAccurateScope scope(&masm, remaining);
    for (int i = 0; i < remaining; ++i) {
      Label target;
      __ b(&target);
      __ bind(&target);
    }
  }

  masm.FinalizeCode();

  return 0;
}