106 lines
2.4 KiB
Forth
106 lines
2.4 KiB
Forth
# slow, iterative divide instruction
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# preconditions: _nr >= 0, _dr > 0
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fn try-divide _nr: int, _dr: int -> result/eax: int {
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# x = next power-of-2 multiple of _dr after _nr
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var x/ecx: int <- copy 1
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{
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#? print-int32-hex 0, x
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#? print-string 0, "\n"
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var tmp/edx: int <- copy _dr
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tmp <- multiply x
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compare tmp, _nr
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break-if->
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x <- shift-left 1
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loop
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}
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#? print-string 0, "--\n"
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# min, max = x/2, x
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var max/ecx: int <- copy x
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var min/edx: int <- copy max
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min <- shift-right 1
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# narrow down result between min and max
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var i/eax: int <- copy min
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{
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#? print-int32-hex 0, i
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#? print-string 0, "\n"
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var foo/ebx: int <- copy _dr
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foo <- multiply i
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compare foo, _nr
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break-if->
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i <- increment
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loop
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}
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result <- copy i
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result <- decrement
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#? print-string 0, "=> "
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#? print-int32-hex 0, result
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#? print-string 0, "\n"
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}
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fn test-try-divide-1 {
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var result/eax: int <- try-divide 0, 2
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check-ints-equal result, 0, "F - try-divide-1"
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}
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fn test-try-divide-2 {
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var result/eax: int <- try-divide 1, 2
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check-ints-equal result, 0, "F - try-divide-2"
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}
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fn test-try-divide-3 {
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var result/eax: int <- try-divide 2, 2
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check-ints-equal result, 1, "F - try-divide-3"
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}
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fn test-try-divide-4 {
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var result/eax: int <- try-divide 4, 2
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check-ints-equal result, 2, "F - try-divide-4"
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}
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fn test-try-divide-5 {
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var result/eax: int <- try-divide 6, 2
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check-ints-equal result, 3, "F - try-divide-5"
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}
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fn test-try-divide-6 {
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var result/eax: int <- try-divide 9, 3
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check-ints-equal result, 3, "F - try-divide-6"
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}
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fn test-try-divide-7 {
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var result/eax: int <- try-divide 0xc, 4
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check-ints-equal result, 3, "F - try-divide-7"
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}
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fn test-try-divide-8 {
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var result/eax: int <- try-divide 0x1b, 3 # 27/3
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check-ints-equal result, 9, "F - try-divide-8"
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}
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fn test-try-divide-9 {
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var result/eax: int <- try-divide 0x1c, 3 # 28/3
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check-ints-equal result, 9, "F - try-divide-9"
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}
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# only positive dr for now
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fn try-modulo nr: int, dr: int -> result/eax: int {
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var _positive-nr/eax: int <- abs nr
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var positive-nr/ecx: int <- copy _positive-nr
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var tmp/eax: int <- try-divide positive-nr, dr
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tmp <- multiply dr
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tmp <- subtract positive-nr
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result <- negate
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}
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fn test-try-modulo-negative-nr {
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var result/eax: int <- try-modulo -0xa, 7
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check-ints-equal result, 3, "F - test-try-modulo-negative-nr"
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}
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fn abs n: int -> result/eax: int {
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result <- copy n
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compare n, 0
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break-if->=
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result <- negate
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}
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