88 lines
2.6 KiB
C
88 lines
2.6 KiB
C
/* $Header$ */
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/* B L O C K S T O R I N G A N D L O A D I N G */
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#include <em.h>
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#include "arith.h"
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#include "sizes.h"
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#include "atw.h"
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/* Because EM does not support the loading and storing of
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objects having other sizes than word fragment and multiple,
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we need to have a way of transferring these objects, whereby
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we simulate "loi" and "sti": the address of the source resp.
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destination is located on top of stack and a call is done
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to load_block() resp. store_block().
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===============================================================
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# Loadblock() works on the stack as follows: ([ ] indicates the
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# position of the stackpointer)
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# lower address--->
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# 1) | &object
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# 2) | ... ATW(sz) bytes ... | sz | &stack_block | &object
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# 3) | ... ATW(sz) bytes ...
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===============================================================
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Loadblock() pushes ATW(sz) bytes directly onto the stack!
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Store_block() works on the stack as follows:
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lower address--->
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1) | ... ATW(sz) bytes ... | &object
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2) | ... ATW(sz) bytes ... | &object | &stack_block | sz
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3) <empty>
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If sz is a legal argument for "loi" or "sti", just one EM
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instruction is generated.
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In the other cases, the notion of alignment is taken into account:
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we only push an object of the size accepted by EM onto the stack,
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while we need a loop to store the stack block into a memory object.
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*/
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store_block(sz, al)
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arith sz;
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int al;
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{
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/* Next condition contains Lots of Irritating Stupid Parentheses
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*/
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if (
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((sz == al) && (word_align % al == 0)) ||
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(
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(sz % word_size == 0 || word_size % sz == 0) &&
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(al % word_align == 0)
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)
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)
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C_sti(sz);
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else {
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/* address of destination lies on the stack */
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/* push address of first byte of block on stack onto
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the stack by computing it from the current stack
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pointer position
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*/
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C_lor((arith)1); /* push current sp */
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C_adp(pointer_size); /* set & to 1st byte of block */
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C_loc(sz); /* number of bytes to transfer */
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C_cal("__stb"); /* call transfer routine */
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C_asp(pointer_size + pointer_size + int_size + ATW(sz));
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}
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}
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load_block(sz, al)
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arith sz;
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int al;
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{
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arith esz = ATW(sz); /* effective size == actual # pushed bytes */
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if ((sz == al) && (word_align % al == 0))
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C_loi(sz);
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else
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if (al % word_align == 0)
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C_loi(esz);
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else {
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/* do not try to understand this... */
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C_asp(-(esz - pointer_size)); /* allocate stack block */
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C_lor((arith)1); /* push & of stack block as dst */
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C_dup(pointer_size); /* fetch source address */
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C_adp(esz - pointer_size);
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C_loi(pointer_size);
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C_loc(sz); /* # bytes to copy */
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C_cal("__stb"); /* library copy routine */
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C_asp(int_size + pointer_size + pointer_size);
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}
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}
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