Experiment with 8-byte integers in ncg i386.
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);
This commit is contained in:
George Koehler
parent
1faff418ec
commit
893df4b79b
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@ -1,7 +1,7 @@
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for _, plat in ipairs(vars.plats) do
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acklibrary {
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name = "lib_"..plat,
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srcs = { "./*.s" },
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srcs = { "./*.s" }, -- dvi8.s
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vars = { plat = plat },
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}
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end
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115
mach/i386/libem/dvi8.s
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115
mach/i386/libem/dvi8.s
Normal file
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@ -0,0 +1,115 @@
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.sect .text; .sect .rom; .sect .data; .sect .bss
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.sect .text
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.define .dvi8, .dvu8
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yl=8
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yh=12
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xl=16
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xh=20
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! .dvi8 and .dvu8 divide x = xh:xl by y = yh:yl,
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! yield edx:eax = quotient, ecx:ebx = remainder.
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.dvu8:
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! Unsigned division: set di = 0 for non-negative quotient.
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push edi
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xor di,di
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mov eax,xh(esp)
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mov edx,yh(esp)
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and edx,edx
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jmp 7f
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.dvi8:
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! Signed division: replace x and y with their absolute values.
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! Set di = 1 for negative quotient, 0 for non-negative.
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push edi
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xor di,di ! di = 0
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mov eax,xh(esp)
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and eax,eax
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jns 1f
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inc di ! di = 1
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neg eax
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neg xl(esp)
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sbb eax,0 ! eax:xl = absolute value of x
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1: mov edx,yh(esp)
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and edx,edx
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jns 7f
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xor di,1 ! flip di
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neg edx
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neg yl(esp)
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sbb edx,0 ! edx:yl = absolute value of y
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7: ! Here .dvu8 joins .dvi8, eax = xh, edx = yh, flags test edx,
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! the values in xh(esp) and yh(esp) are garbage.
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jnz 8f ! jump if y >= 2**32
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! x / y = x / yl = xh / yl + xl / yl = qh + (xl + rh) / yl
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! where qh and rh are quotient, remainder from xh / yl.
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mov ebx,yl(esp)
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xor edx,edx ! edx:eax = xh
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div ebx ! eax = qh, edx = rh
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mov ecx,eax
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mov eax,xl(esp)
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div ebx ! eax = ql, edx = remainder
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mov ebx,edx
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mov edx,ecx ! edx:eax = quotient qh:ql
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xor ecx,ecx ! ecx:ebx = remainder
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9: ! Finally, if di != 0 then negate quotient, remainder.
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and di,di
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jz 1f
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neg edx
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neg eax
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sbb edx,0 ! negate quotient edx:eax
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neg ecx
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neg ebx
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sbb ecx,0 ! negate remainder ecx:ebx
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1: pop edi ! caller's edi
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ret 16
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8: ! We come here if y >= 2**32.
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mov xh(esp),eax
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mov yh(esp),edx
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mov ebx,yl(esp) ! edx:ebx = y
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! Estimate x / y as q = (x / (y >> cl)) >> cl,
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! where 2**31 <= (y >> cl) < 2**32.
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xor cx,cx
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1: inc cx
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shr edx,1
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rcr ebx,1 ! edx:ebx = y >> cl
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and edx,edx
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jnz 1b ! loop until y >> cl fits in ebx
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! x / (y >> cl) = qh + (x + rh) / (y >> cl)
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push edi
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xor edx,edx ! edx:eax = xh
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div ebx ! eax = qh, edx = rh
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mov edi,eax
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mov eax,xl+4(esp) ! push edi moved xl to xl+4
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div ebx ! edi:eax = x / (y >> cl)
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! q = (x / (y >> cl)) >> cl = esi:eax >> cl
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shr eax,cl
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neg cx ! cl = (32 - cl) modulo 32
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shl edi,cl
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or eax,edi ! eax = q
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! Calculate the remainder x - q * y. If the subtraction
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! overflows, then the correct quotient is q - 1, else it is q.
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mov ecx,yh+4(esp)
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imul ecx,eax ! ecx = q * yh
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mov edi,eax
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mul yl+4(esp) ! edx:eax = q * yl
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add edx,ecx ! edx:eax = q * y
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mov ebx,xl+4(esp)
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mov ecx,xh+4(esp) ! ecx:ebx = x
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sub ebx,eax
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sbb ecx,edx ! ecx:ebx = remainder
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jnc 1f
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dec edi ! fix quotient
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add ebx,yl+4(esp)
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adc ebx,yh+4(esp) ! fix remainder
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1: mov eax,edi
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xor edx,edx ! edx:eax = quotient
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pop edi ! negative flag
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jmp 9b
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20
mach/i386/libem/mli8.s
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20
mach/i386/libem/mli8.s
Normal file
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@ -0,0 +1,20 @@
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.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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@ -961,6 +961,14 @@ with EXACT rmorconst const
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uses reusing %1,REG=%1
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gen add %a,%2 yields %a
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pat adi $1==8
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with REG REG rmorconst rmorconst
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gen add %1,%3
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adc %2,%4 yields %2 %1
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with rmorconst rmorconst REG REG
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gen add %3,%1
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adc %4,%2 yields %4 %3
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/*
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pat adi !defined($1)
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with CXREG ACC
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@ -969,13 +977,17 @@ with CXREG ACC
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*/
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pat sbi $1==4
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with rmorconst REG
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gen sub %2,%1 yields %2
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with EXACT REG rmorconst
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gen sub %1,%2
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neg %1 yields %1
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pat sbi $1==8
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with rmorconst rmorconst REG REG
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gen sub %3,%1
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sbb %4,%2 yields %4 %3
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/*
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pat sbi !defined($1)
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with CXREG ACC
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@ -995,6 +1007,11 @@ with rm const
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uses reusing %1,REG
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gen imul %a,%1,%2 yields %a
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pat mli $1==8
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with ACC DXREG
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kills ALL
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gen proccall {label,".mli8"} yields edx eax
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/*
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pat mli !defined($1)
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with ACC
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@ -1008,6 +1025,10 @@ with noacc ACC
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gen cdq.
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idiv %1 yields eax
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pat dvi $1==8
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kills ALL
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gen proccall {label,".dvi8"} yields edx eax
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/*
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pat dvi !defined($1)
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with ACC
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@ -1021,6 +1042,10 @@ with noacc ACC
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gen cdq.
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idiv %1 yields edx
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pat rmi $1==8
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kills ALL
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gen proccall {label,".dvi8"} yields ecx ebx
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/*
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pat rmi !defined($1)
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with ACC
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with REG
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gen neg %1 yields %1
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pat ngi $1==8
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with REG REG
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gen neg %2
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neg %1
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sbb %2,{ANYCON,0} yields %2 %1
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/*
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pat ngi !defined($1)
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with ACC
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@ -1114,6 +1145,10 @@ with noacc ACC
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uses DXREG={ANYCON,0}
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gen div %1 yields eax
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pat dvu $1==8
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kills ALL
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gen proccall {label,".dvu8"} yields edx eax
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/*
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pat dvu !defined($1)
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with ACC STACK
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@ -1126,6 +1161,10 @@ with noacc ACC
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uses DXREG={ANYCON,0}
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gen div %1 yields edx
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pat rmu $1==8
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kills ALL
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gen proccall {label,".dvu8"} yields ecx ebx
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/*
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pat rmu !defined($1)
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with ACC STACK
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