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cordic: vivado is bad at inferring compact adder/subtractor logic

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Robert Jordens 2014-09-03 18:27:13 -06:00 committed by Sebastien Bourdeauducq
parent 4328122a9c
commit 683643266f
1 changed files with 8 additions and 11 deletions
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19
migen/genlib/cordic.py
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@ -285,10 +285,11 @@ class TwoQuadrantCordic(Module):
return a, s, zmax, gain
def _stage(self, xi, yi, zi, xo, yo, zo, i, ai):
dir = Signal()
if self.cordic_mode == "rotate":
direction = zi < 0
self.comb += dir.eq(zi < 0)
else: # vector
direction = yi >= 0
self.comb += dir.eq(yi >= 0)
dx = yi>>i
dy = xi>>i
dz = ai
@ -296,15 +297,11 @@ class TwoQuadrantCordic(Module):
dx = 0
elif self.func_mode == "hyperbolic":
dx = -dx
stmt = If(direction,
xo.eq(xi + dx),
yo.eq(yi - dy),
zo.eq(zi + dz),
).Else(
xo.eq(xi - dx),
yo.eq(yi + dy),
zo.eq(zi - dz),
)
stmt = [
xo.eq(xi + Mux(dir, dx, -dx)),
yo.eq(yi + Mux(dir, -dy, dy)),
zo.eq(zi + Mux(dir, dz, -dz))
]
return stmt
class Cordic(TwoQuadrantCordic):