Help with PASM indirect indexing
Agent420
Posts: 439
As the Prop does not provide offset indexed register accessing, I am trying to determine the best way to modify random elements of an array when I provide the index (or offset) to the desired element...
I have an array of 32 registers (lpix) that may be modified.
I have two 4 register arrays containing the offset (xoff) and the manipulating data (mpix) that needs to be OR'd with the main array (lpix) if a qualifying value is true (y1-y4).·
This is what I have come up with...· It just seems like a lot of work compared to what I'm used to with processors offerring indexed addressing modes.· Is there a better method?
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I have an array of 32 registers (lpix) that may be modified.
I have two 4 register arrays containing the offset (xoff) and the manipulating data (mpix) that needs to be OR'd with the main array (lpix) if a qualifying value is true (y1-y4).·
This is what I have come up with...· It just seems like a lot of work compared to what I'm used to with processors offerring indexed addressing modes.· Is there a better method?
andn y1,missile_ht wz, nr '+4 check if y1 in range
if_z mov lpix_,#lpix '+4 set line pixel base address
if_z add lpix_,xoff '+4 add x1 offset
if_z movd :y1,lpix_ '+4 set lpix dest
nop '+4 movd requires buffer instr
:y1 if_z or lpix,mpix '+4 set pixel
'* 24 (-166)
andn y2,missile_ht wz, nr '+4
if_z mov lpix_,#lpix '+4
if_z add lpix_,xoff+1 '+4
if_z movd :y2,lpix_ '+4
nop '+4 movd requires buffer instr
:y2 if_z or lpix,mpix+1 '+4
' *24 (-142)
andn y3,missile_ht wz, nr '+4
if_z mov lpix_,#lpix '+4
if_z add lpix_,xoff+2 '+4
if_z movd :y3,lpix_ '+4
nop '+4 movd requires buffer instr
:y3 if_z or lpix,mpix+2 '+4
' *24 (-118)
andn y4,missile_ht wz, nr '+4
if_z mov lpix_,#lpix '+4
if_z add lpix_,xoff+3 '+4
if_z movd :y4,lpix_ '+4
nop '+4 movd requires buffer instr
:y4 if_z or lpix,mpix+3 '+4
' *24 (-94)
' Undefined cursor data
x_base res 1
y_base res 1
idx res 1
idy res 1
regs res 1
mpix res 4
mpix_ res 1
xoff res 4
xoff_ res 1
tpix res 1
temp res 1
lpix res 32
lpix_ res 1
frame res 1
y1 res 1
y2 res 1
y3 res 1
y4 res 1
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Comments
setup ' if you run that code once you don't need setup, as the instructions already have the right values movd :yaccess, #y1 mov lpix_, #lpix add lpix_, xoff movd :y1, lpix_ movs :y1, #mpix setup_done mov lp_counter, #3 :yaccess andn y1,missile_ht wz, nr ' add :y1, inc_dest_n_src ' this is for not wasting the memory with a NOP - note: this will take effect for the next loop :y1 if_z or lpix,mpix ' add :yaccess, inc_dest djnz :yaccess, lp_counter ' maybe this one is wrong order?? First lp_counter then :yaccess ... (long time not coded in PASM ;o) inc_dest_n_src long %000000001_000000001 inc_dest long %000000001_000000000 ' here comes your res part ......Something like that. You have to debug it by yourself ;o) .. unless til I'm back home.
Post Edited (MagIO2) : 9/9/2009 11:53:02 AM GMT
My problem is that while the y1..y4 and xoff are sequential, the resulting lpix destination will not be (because it is the result of xoff+#lpix and the offset will be different for every value... ie xoff = 1,5,3,2), so I cannot simply incrementally update the lpix destination in your y1: line.
But you did get me thinking that perhaps I can add the #lpix base address in the area where I am calculating the offset, so I would be storing the lpix addresses I need to reference rather than just the offset (and subsequently needing to calculate the destination address in my example).
Thanks for your input.
·
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movd :y1,#y1 'init y1 base movd :y2,#xoff 'init xoff base movs :y2,#mpix 'init mpix base mov idx,#4 'start loop y1: andn y1,missile_ht wz, nr 'test cond y2: if_z or xoff,mpix 'process add :y1,d1 'incr y1 dest +1 add :y2,d1s1 'incr y2 dest,source djnz idx,#:y1 'loop d1s1 long 1 << 9 + 1 'd+1, s+1 d1 long 1 << 9 'd+1But in regards to my original question, if you do need to randomly reference addresses, I guess you would accomplish it by doing the math and then self modifying the code as I did?
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I think I have to revert to my original example...· In the revised code, incrementing the destination at :y2 will only result in incrementing the existing address, rather than going to address at xoff+1.
ie #lpix = $080
xoff = $080, 083, 090, 087
··············· movd··· :y2,xoff·············· 'init xoff base
··············· movs··· :y2,#mpix·············'init mpix base
y2:···· if_z··or········xoff,mpix·············· 'process
··············· add···· :y2,d1s1··············· 'incr y2 dest,source
First time through, :y2 is ok (or $080,mpix).· But then it just gets incremented to $081 rather than $083 where I need it to be.
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Post Edited (Agent420) : 9/9/2009 1:33:41 PM GMT