hdl.ast: add Value.xor, mapping to $reduce_xor.

Fixes #147.
2019-09-13 14:28:43 +00:00 · 2019-09-13 14:28:43 +00:00 · 32310aecad
commit 32310aecad
parent b23a9794a4
4 changed files with 23 additions and 0 deletions
--- a/nmigen/back/pysim.py
+++ b/nmigen/back/pysim.py
@ -135,6 +135,9 @@ class _RHSValueCompiler(_ValueCompiler):
                val, = value.operands
                mask = (1 << len(val)) - 1
                return lambda state: normalize(arg(state) == mask, shape)
+            if value.op == "r^":
+                # Believe it or not, this is the fastest way to compute a sideways XOR in Python.
+                return lambda state: normalize(str(arg(state)).count("1") % 2, shape)
        elif len(value.operands) == 2:
            lhs, rhs = map(self, value.operands)
            if value.op == "+":