swap-int32.cc

// Copyright 2014, ARM Limited
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#include "examples.h"

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

void GenerateSwapInt32(MacroAssembler* masm) {
  {
    // In this scope the register x2 will be used by the macro-assembler
    // as the stack pointer (via peek, poke, push, etc).
    const Register old_stack_pointer = __ StackPointer();
    __ Mov(x2, __ StackPointer());
    __ SetStackPointer(x2);

    // This call to Claim is not 16-byte aligned and would have failed
    // if the current stack pointer was sp.
    __ Claim(8);

    __ Poke(w0, 0);
    __ Poke(w1, 4);
    __ Peek(w1, 0);
    __ Peek(w0, 4);

    __ Drop(8);

    // Even if we didn't use the system stack pointer, sp might have been
    // modified because the ABI forbids access to memory below the stack
    // pointer.
    __ Mov(old_stack_pointer, __ StackPointer());
    __ SetStackPointer(old_stack_pointer);
  }

  // The stack pointer has now been switched back to sp.
  __ Ret();
}


#ifndef TEST_EXAMPLES
#ifdef USE_SIMULATOR
int main(void) {
  // Create and initialize the assembler and the simulator.
  byte assm_buf[BUF_SIZE];
  MacroAssembler masm(assm_buf, BUF_SIZE);
  Decoder decoder;
  Simulator simulator(&decoder);

  // Generate the code for the example function.
  Label swap_int32;
  masm.Bind(&swap_int32);
  GenerateSwapInt32(&masm);
  masm.FinalizeCode();

  // Run the example function.
  simulator.set_wreg(0, 0x11111111);
  simulator.set_wreg(1, 0x22222222);

  printf("Before swap_int32:\n"
         "x0 = 0x%" PRIx32 "\n"
         "x1 = 0x%" PRIx32 "\n",
         simulator.wreg(0), simulator.wreg(1));

  simulator.RunFrom(masm.GetLabelAddress<Instruction*>(&swap_int32));

  printf("After swap_int32:\n"
         "x0 = 0x%" PRIx32 "\n"
         "x1 = 0x%" PRIx32 "\n",
         simulator.wreg(0), simulator.wreg(1));

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