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47 lines
1.3 KiB
Python
47 lines
1.3 KiB
Python
from __future__ import generators
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from myhdl import Signal, intbv
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from arith_utils import log2ceil
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from arith_utils import SLOW, MEDIUM, FAST
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def PrefixAnd(width, speed, PI, PO):
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n = width
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m = log2ceil(width)
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def fastPrefix():
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PT = Signal(intbv())
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while 1:
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yield PI, PT
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PT.next[n:] = PI
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for l in range(1, m+1):
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for k in range(2**(m-l)):
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for i in range(2**(l-1)):
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if (k*2**l + i) < n:
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PT.next[l*n + k*2**l + i] = \
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PT[(l-1)*n + k*2**l + i]
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if (k*2**l + 2**(l-1) + i) < n:
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PT.next[l*n + k*2**l + 2**(l-1) + i] = \
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PT[(l-1)*n + k*2**l + 2**(l-1) + i] & \
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PT[(l-1)*n + k*2**l + 2**(l-1) - 1]
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PO.next = PT[(m+1)*n:m*n]
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def slowPrefix():
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PT = Signal(intbv())
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while 1:
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yield PI, PT
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PT.next[0] = PI[0]
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for i in range(1, n):
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PT.next[i] = PI[i] & PT[i-1]
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PO.next = PT
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if speed == SLOW:
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return slowPrefix()
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elif speed == FAST:
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return fastPrefix()
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else:
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raise NotImplementedError
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