pcsx2/common/src/x86emitter/jmp.cpp

/*  PCSX2 - PS2 Emulator for PCs
 *  Copyright (C) 2002-2009  PCSX2 Dev Team
 * 
 *  PCSX2 is free software: you can redistribute it and/or modify it under the terms
 *  of the GNU Lesser General Public License as published by the Free Software Found-
 *  ation, either version 3 of the License, or (at your option) any later version.
 *
 *  PCSX2 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 PCSX2.
 *  If not, see <http://www.gnu.org/licenses/>.
 */

/*
 * ix86 core v0.9.1
 *
 * Original Authors (v0.6.2 and prior):
 *		linuzappz <linuzappz@pcsx.net>
 *		alexey silinov
 *		goldfinger
 *		zerofrog(@gmail.com)
 *
 * Authors of v0.9.1:
 *		Jake.Stine(@gmail.com)
 *		cottonvibes(@gmail.com)
 *		sudonim(1@gmail.com)
 */

#include "PrecompiledHeader.h"
#include "internal.h"

namespace x86Emitter {

void xImpl_JmpCall::operator()( const xRegister32& absreg ) const	{ xOpWrite( 0x00, 0xff, isJmp ? 4 : 2, absreg ); }
void xImpl_JmpCall::operator()( const ModSib32& src ) const			{ xOpWrite( 0x00, 0xff, isJmp ? 4 : 2, src ); }

void xImpl_JmpCall::operator()( const xRegister16& absreg ) const	{ xOpWrite( 0x66, 0xff, isJmp ? 4 : 2, absreg ); }
void xImpl_JmpCall::operator()( const ModSib16& src ) const			{ xOpWrite( 0x66, 0xff, isJmp ? 4 : 2, src ); }

const xImpl_JmpCall xJMP	= { true };
const xImpl_JmpCall xCALL	= { false };

void xSmartJump::SetTarget()
{
	u8* target = xGetPtr();
	if( m_baseptr == NULL ) return;

	xSetPtr( m_baseptr );
	u8* const saveme = m_baseptr + GetMaxInstructionSize();
	xJccKnownTarget( m_cc, target, true );

	// Copy recompiled data inward if the jump instruction didn't fill the
	// alloted buffer (means that we optimized things to a j8!)

	const int spacer = (sptr)saveme - (sptr)xGetPtr();
	if( spacer != 0 )
	{
		u8* destpos = xGetPtr();
		const int copylen = (sptr)target - (sptr)saveme;

		memcpy_fast( destpos, saveme, copylen );
		xSetPtr( target - spacer );
	}
}

xSmartJump::~xSmartJump()
{
	SetTarget();
	m_baseptr = NULL;	// just in case (sometimes helps in debugging too)
}

// ------------------------------------------------------------------------
// Emits a 32 bit jump, and returns a pointer to the 32 bit displacement.
// (displacements should be assigned relative to the end of the jump instruction,
// or in other words *(retval+1) )
__emitinline s32* xJcc32( JccComparisonType comparison, s32 displacement )
{
	if( comparison == Jcc_Unconditional )
		xWrite8( 0xe9 );
	else
	{
		xWrite8( 0x0f );
		xWrite8( 0x80 | comparison );
	}
	xWrite<s32>( displacement );

	return ((s32*)xGetPtr()) - 1;
}

// ------------------------------------------------------------------------
// Emits a 32 bit jump, and returns a pointer to the 8 bit displacement.
// (displacements should be assigned relative to the end of the jump instruction,
// or in other words *(retval+1) )
__emitinline s8* xJcc8( JccComparisonType comparison, s8 displacement )
{
	xWrite8( (comparison == Jcc_Unconditional) ? 0xeb : (0x70 | comparison) );
	xWrite<s8>( displacement );
	return (s8*)xGetPtr() - 1;
}

// ------------------------------------------------------------------------
// Writes a jump at the current x86Ptr, which targets a pre-established target address.
// (usually a backwards jump)
//
// slideForward - used internally by xSmartJump to indicate that the jump target is going
// to slide forward in the event of an 8 bit displacement.
//
__emitinline void xJccKnownTarget( JccComparisonType comparison, const void* target, bool slideForward )
{
	// Calculate the potential j8 displacement first, assuming an instruction length of 2:
	sptr displacement8 = (sptr)target - (sptr)(xGetPtr() + 2);

	const int slideVal = slideForward ? ((comparison == Jcc_Unconditional) ? 3 : 4) : 0;
	displacement8 -= slideVal;

	if( slideForward ) 
	{
		pxAssertDev( displacement8 >= 0, "Used slideForward on a backward jump; nothing to slide!" );
	}
	
	if( is_s8( displacement8 ) )
		xJcc8( comparison, displacement8 );
	else
	{
		// Perform a 32 bit jump instead. :(
		s32* bah = xJcc32( comparison );
		*bah = (s32)target - (s32)xGetPtr();
	}
}

// Low-level jump instruction!  Specify a comparison type and a target in void* form, and
// a jump (either 8 or 32 bit) is generated.
__emitinline void xJcc( JccComparisonType comparison, const void* target )
{
	xJccKnownTarget( comparison, target, false );
}

xForwardJumpBase::xForwardJumpBase( uint opsize, JccComparisonType cctype )
{
	pxAssert( opsize == 1 || opsize == 4 );
	pxAssertDev( cctype != Jcc_Unknown, "Invalid ForwardJump conditional type." );

	BasePtr = (s8*)xGetPtr() +
		((opsize == 1) ? 2 :					// j8's are always 2 bytes.
		((cctype==Jcc_Unconditional) ? 5 : 6 ));	// j32's are either 5 or 6 bytes

	if( opsize == 1 )
		xWrite8( (cctype == Jcc_Unconditional) ? 0xeb : (0x70 | cctype) );
	else
	{
		if( cctype == Jcc_Unconditional )
			xWrite8( 0xe9 );
		else
		{
			xWrite8( 0x0f );
			xWrite8( 0x80 | cctype );
		}
	}

	xAdvancePtr( opsize );
}

void xForwardJumpBase::_setTarget( uint opsize ) const
{
	pxAssertDev( BasePtr != NULL, "" );

	sptr displacement = (sptr)xGetPtr() - (sptr)BasePtr;
	if( opsize == 1 )
	{
		pxAssertDev( is_s8( displacement ), "Emitter Error: Invalid short jump displacement." );
		BasePtr[-1] = (s8)displacement;
	}
	else
	{
		// full displacement, no sanity checks needed :D
		((s32*)BasePtr)[-1] = displacement;
	}
}

// returns the inverted conditional type for this Jcc condition.  Ie, JNS will become JS.
__forceinline JccComparisonType xInvertCond( JccComparisonType src )
{
	pxAssert( src != Jcc_Unknown );
	if( Jcc_Unconditional == src ) return Jcc_Unconditional;

	// x86 conditionals are clever!  To invert conditional types, just invert the lower bit:
	return (JccComparisonType)((int)src ^ 1);
}

}