ack/lang/cem/cemcom/blocks.c

/*
 * (c) copyright 1987 by the Vrije Universiteit, Amsterdam, The Netherlands.
 * See the copyright notice in the ACK home directory, in the file "Copyright".
 */
/* $Header$ */
/*	B L O C K   S T O R I N G   A N D   L O A D I N G	*/

#include <em.h>
#include "arith.h"
#include "sizes.h"
#include "atw.h"
#ifndef STB
#include "label.h"
#include "stack.h"
#endif STB

/*	Because EM does not support the loading and storing of
	objects having other sizes than word fragment and multiple,
	we need to have a way of transferring these objects, whereby
	we simulate "loi" and "sti": the address of the source resp.
	destination is located on top of stack and a call is done
	to load_block() resp. store_block().
	===============================================================
	# Loadblock() works on the stack as follows: ([ ] indicates the
	# position of the stackpointer)
	# lower address--->
	# 1)	| &object
	# 2)	| ... ATW(sz) bytes ... | sz | &stack_block | &object
	# 3)	| ... ATW(sz) bytes ...
	===============================================================
	Loadblock() pushes ATW(sz) bytes directly onto the stack!

	Store_block() works on the stack as follows:
	lower address--->
	1)	| ... ATW(sz) bytes ... | &object
	2)	| ... ATW(sz) bytes ... | &object | &stack_block | sz
	3)	<empty>

	If sz is a legal argument for "loi" or "sti", just one EM
	instruction is generated.
	In the other cases, the notion of alignment is taken into account:
	we only push an object of the size accepted by EM onto the stack,
	while we need a loop to store the stack block into a memory object.
*/
store_block(sz, al)
	arith sz;
	int al;
{
	if (
		((sz == al) && (word_align % al == 0)) ||
		(
			(sz % word_size == 0 || word_size % sz == 0) &&
			(al % word_align == 0)
		)
	)	/* Lots of Irritating Stupid Parentheses */
		C_sti(sz);
	else {
#ifndef STB
		arith src, dst, src_offs, dst_offs;

		/* allocate two pointer temporaries */
		src = tmp_pointer_var(&src_offs);
		dst = tmp_pointer_var(&dst_offs);

		/* load the addresses */
		C_lal(dst);
		C_sti(pointer_size);
		C_lor((arith)1);	/* push current sp */
		C_lal(src);
		C_sti(pointer_size);
		copy_loop(sz, src, dst);
		C_asp(ATW(sz));
		free_tmp_var(dst_offs);
		free_tmp_var(src_offs);
#else STB
		/*	address of destination lies on the stack	*/

		/*	push address of first byte of block on stack onto
			the stack by computing it from the current stack
			pointer position
		*/
		C_lor((arith)1);	/* push current sp		*/
		C_adp(pointer_size);	/* set & to 1st byte of block	*/
		C_loc(sz);		/* number of bytes to transfer	*/
		C_cal("__stb");		/* call transfer routine	*/
		C_asp(pointer_size + pointer_size + int_size + ATW(sz));
#endif STB
	}
}

load_block(sz, al)
	arith sz;
	int al;
{
	arith esz = ATW(sz);	/* effective size == actual # pushed bytes */

	if ((sz == al) && (word_align % al == 0))
		C_loi(sz);
	else
	if (al % word_align == 0)
		C_loi(esz);
	else {
#ifndef STB
		arith src, dst, src_offs, dst_offs;

		/* allocate two pointer temporaries */
		src = tmp_pointer_var(&src_offs);
		dst = tmp_pointer_var(&dst_offs);

		C_lal(src);
		C_sti(pointer_size);
		C_asp(-esz);		/* allocate stack block */
		C_lor((arith)1);	/* push & of stack block as dst	*/
		C_lal(dst);
		C_sti(pointer_size);
		copy_loop(sz, src, dst);
		free_tmp_var(dst_offs);
		free_tmp_var(src_offs);
#else STB
		C_asp(-(esz - pointer_size));	/* allocate stack block */
		C_lor((arith)1);	/* push & of stack block as dst	*/
		C_dup(pointer_size);		/* fetch source address	*/
		C_adp(esz - pointer_size);
		C_loi(pointer_size);
		C_loc(sz);			/* # bytes to copy	*/
		C_cal("__stb");			/* library copy routine	*/
		C_asp(int_size + pointer_size + pointer_size);
#endif STB
	}
}

#ifndef STB
copy_loop(sz, src, dst)
	arith sz, src, dst;
{
	/* generate inline byte-copy loop */
	label l_cont = text_label(), l_stop = text_label();

	C_loc(sz);		/* amount of bytes */
	C_df_ilb(l_cont);
	C_dup(word_size);
	C_zle(l_stop);
	C_dec();
	C_lal(src);
	C_loi(pointer_size);
	C_dup(pointer_size);
	C_adp((arith)1);
	C_lal(src);
	C_sti(pointer_size);
	C_loi((arith)1);
	C_lal(dst);
	C_loi(pointer_size);
	C_dup(pointer_size);
	C_adp((arith)1);
	C_lal(dst);
	C_sti(pointer_size);
	C_sti((arith)1);
	C_bra(l_cont);
	C_df_ilb(l_stop);
	C_asp(word_size);
}
#endif STB