dolphin/Source/Core/DSPCore/Src/DSPInterpreter.cpp

/*====================================================================

   filename:     gdsp_interpreter.cpp
   project:      GCemu
   created:      2004-6-18
   mail:		  duddie@walla.com

   Copyright (c) 2005 Duddie & Tratax

   This program is free software; you can redistribute it and/or
   modify it under the terms of the GNU General Public License
   as published by the Free Software Foundation; either version 2
   of the License, or (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.

   ====================================================================*/

#include <stdio.h>
#include <stdlib.h>

#include "DSPTables.h"
#include "DSPHost.h"
#include "DSPCore.h"
#include "DSPAnalyzer.h"

#include "gdsp_interface.h"
#include "DSPIntUtil.h"

namespace DSPInterpreter {

volatile u32 gdsp_running;

// NOTE: These have nothing to do with g_dsp.r[DSP_REG_CR].

// Hm, should instructions that change CR use this? Probably not (but they
// should call UpdateCachedCR())
void WriteCR(u16 val)
{
	// reset
	if (val & 0x0001)
	{
		DSPCore_Reset();
	}

	val &= ~0x0001;

	// update cr
	g_dsp.cr = val;
}

// Hm, should instructions that read CR use this? (Probably not).
u16 ReadCR()
{
	if (g_dsp.pc & 0x8000)
	{
		g_dsp.cr |= 0x800;
	}
	else
	{
		g_dsp.cr &= ~0x800;
	}

	return g_dsp.cr;
}



void HandleLoop()
{
	// Handle looping hardware. 
	u16& rLoopCounter = g_dsp.r[DSP_REG_ST3];
	if (rLoopCounter > 0)
	{
		const u16 rCallAddress = g_dsp.r[DSP_REG_ST0];
		const u16 rLoopAddress = g_dsp.r[DSP_REG_ST2];

		// This does not always work correctly!
		// The loop end tends to point to the second part of 
		// two-byte instructions!
		if (g_dsp.pc == (rLoopAddress + 1))
		{
			rLoopCounter--;
			if (rLoopCounter > 0)
			{
				g_dsp.pc = rCallAddress;
			}
			else
			{
				// end of loop
				dsp_reg_load_stack(0);
				dsp_reg_load_stack(2);
				dsp_reg_load_stack(3);
			}
		}
	}
}

void Step()
{
	DSPCore_CheckExceptions();

	g_dsp.step_counter++;

#if PROFILE
	g_dsp.err_pc = g_dsp.pc;

	ProfilerAddDelta(g_dsp.err_pc, 1);
	if (g_dsp.step_counter == 1)
	{
		ProfilerInit();
	}

	if ((g_dsp.step_counter & 0xFFFFF) == 0)
	{
		ProfilerDump(g_dsp.step_counter);
	}
#endif

	u16 opc = dsp_fetch_code();
	ExecuteInstruction(UDSPInstruction(opc));
	HandleLoop();
}

// Used by thread mode.
void Run()
{
	gdsp_running = true;
	while (!(g_dsp.cr & CR_HALT))
	{
		// Are we running?
		if (DSPHost_Running())
			break;

		DSPCore_CheckExternalInterrupt();
		// This number (500) is completely arbitrary. TODO: tweak.
		for (int i = 0; i < 500 && !(g_dsp.cr & CR_HALT); i++)
			Step();

		if (!gdsp_running)
			break;
	}
	gdsp_running = false;
}

// Used by non-thread mode.
void RunCycles(int cycles)
{
	if (cycles < 18)
	{
		for (int i = 0; i < cycles; i++)
		{
			if (g_dsp.cr & CR_HALT)
				return;
			if (DSPAnalyzer::code_flags[g_dsp.pc] & DSPAnalyzer::CODE_IDLE_SKIP)
				return;
			Step();
			cycles--;
		}
		return;
	}


	DSPCore_CheckExternalInterrupt();

	// First, let's run a few cycles with no idle skipping so that things can progress a bit.
	for (int i = 0; i < 8; i++)
	{
		if (g_dsp.cr & CR_HALT)
			return;
		Step();
		cycles--;
	}

	// Next, let's run a few cycles with idle skipping, so that we can skip idle loops.
	for (int i = 0; i < 8; i++)
	{
		if (g_dsp.cr & CR_HALT)
			return;
		if (DSPAnalyzer::code_flags[g_dsp.pc] & DSPAnalyzer::CODE_IDLE_SKIP)
			return;
		Step();
		cycles--;
	}

	// Now, run the rest of the block without idle skipping. It might trip into a 
	// idle loop and if so we waste some time here. Might be beneficial to slice even further.
	while (cycles > 0)
	{
		Step();
		cycles--;
		// We don't bother directly supporting pause - if the main emu pauses,
		// it just won't call this function anymore.
	}
}

void Stop()
{
	gdsp_running = false;
}

}  // namespace