add nmigen alu_hier to experiment

diff --git a/src/experiment/alu_hier.py b/src/experiment/alu_hier.py
new file mode 100644 (file)
index 0000000..1fc7ea0
--- /dev/null
+++ b/src/experiment/alu_hier.py
@@ -0,0 +1,58 @@
+from nmigen import Elaboratable, Signal, Module
+from nmigen.cli import main
+
+
+class Adder(Elaboratable):
+    def __init__(self, width):
+        self.a   = Signal(width)
+        self.b   = Signal(width)
+        self.o   = Signal(width)
+
+    def elaborate(self, platform):
+        m = Module()
+        m.d.comb += self.o.eq(self.a + self.b)
+        return m
+
+
+class Subtractor(Elaboratable):
+    def __init__(self, width):
+        self.a   = Signal(width)
+        self.b   = Signal(width)
+        self.o   = Signal(width)
+
+    def elaborate(self, platform):
+        m = Module()
+        m.d.comb += self.o.eq(self.a - self.b)
+        return m
+
+
+class ALU(Elaboratable):
+    def __init__(self, width):
+        self.op  = Signal()
+        self.a   = Signal(width)
+        self.b   = Signal(width)
+        self.o   = Signal(width)
+
+        self.add = Adder(width)
+        self.sub = Subtractor(width)
+
+    def elaborate(self, platform):
+        m = Module()
+        m.submodules.add = self.add
+        m.submodules.sub = self.sub
+        m.d.comb += [
+            self.add.a.eq(self.a),
+            self.sub.a.eq(self.a),
+            self.add.b.eq(self.b),
+            self.sub.b.eq(self.b),
+        ]
+        with m.If(self.op):
+            m.d.comb += self.o.eq(self.sub.o)
+        with m.Else():
+            m.d.comb += self.o.eq(self.add.o)
+        return m
+
+
+if __name__ == "__main__":
+    alu = ALU(width=16)
+    main(alu, ports=[alu.op, alu.a, alu.b, alu.o])