/**
 * \file
 * <!--
 * This file is part of BeRTOS.
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 * Copyright 2008 Bernie Innocenti <bernie@codewiz.org>
 * -->
 *
 * \author Bernie Innocenti <bernie@codewiz.org>
 *
 * \brief PowerPC context switch
 */

#ifdef __APPLE__
    //This workaround is necessary to compile under OS X assembler.
    #define SWITCH_CONTEXT _asm_switch_context
#else
    #define SWITCH_CONTEXT asm_switch_context
#endif

.balign 4

/* void asm_switch_context(void ** new_sp, void ** save_sp) */
/*                                 r3              r4       */
.globl SWITCH_CONTEXT
SWITCH_CONTEXT:
	mflr	0		/* r0 = lr */
	stw	0,8(1)		/* store lr at *(sp+8) */
	stw	1,0(4)		/* *save_sp = sp */
	lwz	1,0(3)		/* sp = *new_sp */
	lwz	0,8(1)		/* retrieve lr from *(sp+8) */
	mtlr	0		/* lr = r0 */
	blr			/* return */