corelogic: support reverse in displacer/chooser

diff --git a/migen/corelogic/misc.py b/migen/corelogic/misc.py
index ba30e66ee916dfa1ca51ca967be05d1af81a07f5..a6374c51780c940c5c53878843fa8a093eb9fa30 100644 (file)
--- a/migen/corelogic/misc.py
+++ b/migen/corelogic/misc.py
@@ -40,17 +40,27 @@ def split(v, *counts):
                offset += n
        return tuple(r)
 
-def displacer(signal, shift, output, n=None):
+def displacer(signal, shift, output, n=None, reverse=False):
        if n is None:
                n = 2**shift.bv.width
        w = signal.bv.width
-       l = [Replicate(shift == i, w) & signal for i in range(n)]
+       if reverse:
+               r = reversed(range(n))
+       else:
+               r = range(n)
+       l = [Replicate(shift == i, w) & signal for i in r]
        return output.eq(Cat(*l))
 
-def chooser(signal, shift, output, n=None):
+def chooser(signal, shift, output, n=None, reverse=False):
        if n is None:
                n = 2**shift.bv.width
        w = output.bv.width
-       cases = [[Constant(i, shift.bv), output.eq(signal[i*w:(i+1)*w])] for i in range(n)]
+       cases = []
+       for i in range(n):
+               if reverse:
+                       s = n - i - 1
+               else:
+                       s = i
+               cases.append([Constant(i, shift.bv), output.eq(signal[s*w:(s+1)*w])])
        cases[n-1][0] = Default()
        return Case(shift, *cases)