forked from M-Labs/artiq
dsp: add limits support to SatAddMixin
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@ -29,21 +29,33 @@ def eqh(a, b):
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class SatAddMixin:
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def sat_add(self, a):
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"""Signed saturating addition mixin"""
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def sat_add(self, *a, limits=None, clipped=None):
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a = list(a)
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# assert all(value_bits_sign(ai)[1] for ai in a)
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n = max(len(ai) for ai in a)
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o = log2_int(len(a), need_pow2=False)
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s = Signal((n + o, True))
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s0 = Signal((n, True))
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z = Signal((1, True))
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length = max(len(ai) for ai in a)
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carry = log2_int(len(a), need_pow2=False)
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full = Signal((length + carry, True))
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limited = Signal((length, True))
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clip = Signal(2)
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if clipped is not None:
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clipped.eq(clip)
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self.comb += [
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s.eq(reduce(add, a, z)),
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s0[-1].eq(s[-1]),
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If(s[-o-1:] == Replicate(s[-1], o + 1),
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s0[:-1].eq(s[:n-1]),
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).Else(
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s0[:-1].eq(Replicate(~s[-1], n - 1)),
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)
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full.eq(reduce(add, a)),
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]
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return s0
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if limits is None:
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self.comb += [
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If(full[-1-carry:] == Replicate(full[-1], carry + 1),
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limited.eq(full),
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clip.eq(0),
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).Else(
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limited.eq(Cat(Replicate(~full[-1], length - 1), full[-1])),
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clip.eq(Cat(full[-1], ~full[-1])),
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)
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]
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else:
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self.comb += [
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clip.eq(Cat(full < limits[0], full > limits[1])),
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limited.eq(Array([full, limits[0], limits[1], 0])[clip]),
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]
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return limited
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