893df4b79b
This provides adi, sbi, mli, dvi, rmi, ngi, dvu, rmu 8, but is missing
shifts and rotates. It is also missing conversions between 8-byte
integers and other sizes of integers or floats. The code might not be
all correct, but works at least some of the time.
I adapted this from how ncg i86 does 4-byte integers, but I use a
different algorithm when dividing by a large value: i86 avoids the div
instruction and uses a shift-and-subtract loop; but I use the div
instruction to estimate a quotient, which is more like how big integer
libraries do division. My .dvi8 and .dvu8 also set ecx:ebx to the
remainder; this might be a bad idea, because it requires .dvi8 and
.dvu8 to always calculate the remainder, even when the caller only
wants the quotient.
To play with 8-byte integers, I wrote EM procedures like
mes 2, 4, 4
exp $ngi
pro $ngi,0
ldl 4
ngi 8
lol 0
sti 8
lol 0
ret 4
end
exp $adi
pro $adi,0
ldl 4
ldl 12
adi 8
lol 0
sti 8
lol 0
ret 4
end
and called them from C like
typedef struct { int l; int h; } q;
q ngi(q);
q adi(q, q);
21 lines
408 B
ArmAsm
21 lines
408 B
ArmAsm
.sect .text; .sect .rom; .sect .data; .sect .bss
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.sect .text
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.define .mli8
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yl=4
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yh=8
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! xl in eax
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! xh in edx
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.mli8:
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! x * y = (xh + xl) * (yh + yl)
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! = xh * yh + xh * yl + xl * yh + xl * yl
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! The term xh * yh overflows to zero.
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mov ecx,eax
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imul ecx,yh(esp) ! ecx = xl * yh
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imul edx,yl(esp) ! edx = xh * yl
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add ecx,edx
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mul yl(esp) ! edx:eax = xl * yl
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add edx,ecx ! edx:eax = x * y
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ret 8
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