/* src/vm/jit/powerpc/md.c - machine dependent PowerPC functions

   Copyright (C) 1996-2005, 2006, 2007 R. Grafl, A. Krall, C. Kruegel,
   C. Oates, R. Obermaisser, M. Platter, M. Probst, S. Ring,
   E. Steiner, C. Thalinger, D. Thuernbeck, P. Tomsich, C. Ullrich,
   J. Wenninger, Institut f. Computersprachen - TU Wien

   This file is part of CACAO.

   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, 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., 51 Franklin Street, Fifth Floor, Boston, MA
   02110-1301, USA.

*/


#include "config.h"

#include <assert.h>
#include <stdint.h>

#include "vm/types.h"

#include "md-abi.h"
#include "vm/jit/powerpc/codegen.h"
#include "vm/jit/powerpc/md.h"

#include "vm/global.h"
#include "vm/vm.h"

#include "vm/jit/jit.h"


/* md_init *********************************************************************

   Do some machine dependent initialization.

*******************************************************************************/

void md_init(void)
{
	/* nothing to do */
}


/* md_jit_method_patch_address *************************************************

   Gets the patch address of the currently compiled method. The offset
   is extracted from the load instruction(s) before the jump and added
   to the right base address (PV or REG_METHODPTR).

   INVOKESTATIC/SPECIAL:

   81adffd4    lwz     r13,-44(r13)
   7da903a6    mtctr   r13
   4e800421    bctrl

   INVOKEVIRTUAL:

   81830000    lwz     r12,0(r3)
   81ac0000    lwz     r13,0(r12)
   7da903a6    mtctr   r13
   4e800421    bctrl

   INVOKEINTERFACE:

   81830000    lwz     r12,0(r3)
   818c0000    lwz     r12,0(r12)
   81ac0000    lwz     r13,0(r12)
   7da903a6    mtctr   r13
   4e800421    bctrl

*******************************************************************************/

void *md_jit_method_patch_address(void *pv, void *ra, void *mptr)
{
	uint32_t *pc;
	uint32_t  mcode;
	int32_t   offset;
	void     *pa;

	/* go back to the actual load instruction (3 instructions) */

	pc = ((uint32_t *) ra) - 3;

	/* get first instruction word (lwz) */

	mcode = *pc;

	/* check if we have 2 instructions (addis, addi) */

	if ((mcode >> 16) == 0x3c19) {
		/* XXX write a regression for this */
		pa = NULL;
		assert(0);

		/* get displacement of first instruction (addis) */

		offset = (int32_t) (mcode << 16);

		/* get displacement of second instruction (addi) */

		mcode = *(pc + 1);

		assert((mcode >> 16) != 0x6739);

		offset += (int16_t) (mcode & 0x0000ffff);
	}
	else {
		/* get the offset from the instruction */

		offset = (int16_t) (mcode & 0x0000ffff);

		/* check for load from PV */

		if ((mcode >> 16) == 0x81ad) {
			/* get the final data segment address */

			pa = ((uint8_t *) pv) + offset;
		}
		else if ((mcode >> 16) == 0x81ac) {
			/* in this case we use the passed method pointer */

			/* return NULL if no mptr was specified (used for replacement) */

			if (mptr == NULL)
				return NULL;

			pa = ((uint8_t *) mptr) + offset;
		}
		else {
			/* catch any problems */

			vm_abort("md_jit_method_patch_address: unknown instruction %x",
					 mcode);

			/* keep compiler happy */

			pa = NULL;
		}
	}

	return pa;
}


/* md_patch_replacement_point **************************************************

   Patch the given replacement point.

*******************************************************************************/

#if defined(ENABLE_REPLACEMENT)
void md_patch_replacement_point(u1 *pc, u1 *savedmcode, bool revert)
{
	u4 mcode;

	if (revert) {
		/* restore the patched-over instruction */
		*(u4*)(pc) = *(u4*)(savedmcode);
	}
	else {
		/* save the current machine code */
		*(u4*)(savedmcode) = *(u4*)(pc);

		/* build the machine code for the patch */
		assert(0); /* XXX build trap instruction below */
		mcode = 0;

		/* write the new machine code */
		*(u4*)(pc) = (u4) mcode;
	}
	
	/* flush instruction cache */
    md_icacheflush(pc,4);
}
#endif /* defined(ENABLE_REPLACEMENT) */


/*
 * These are local overrides for various environment variables in Emacs.
 * Please do not remove this and leave it at the end of the file, where
 * Emacs will automagically detect them.
 * ---------------------------------------------------------------------
 * Local variables:
 * mode: c
 * indent-tabs-mode: t
 * c-basic-offset: 4
 * tab-width: 4
 * End:
 * vim:noexpandtab:sw=4:ts=4:
 */
