Add @cliffordwolf freduce testcase

tests/various/muxpack.v

@@ -166,3 +166,16 @@ module cliffordwolf_nonexclusive_select (
                 if (z) o = d;
         end
 endmodule
+
+module cliffordwolf_freduce (
+        input wire [1:0] s,
+        input wire a, b, c, d,
+        output reg [3:0] o
+);
+        always @* begin
+                o = {4{a}};
+                if (s == 0) o = {3{b}};
+                if (s == 1) o = {2{c}};
+                if (s == 2) o = d;
+        end
+endmodule

tests/various/muxpack.ys

@@ -178,3 +178,20 @@ design -import gold -as gold
 design -import gate -as gate
 miter -equiv -flatten -make_assert -make_outputs gold gate miter
 sat -verify -prove-asserts -show-ports miter
+
+design -load read
+hierarchy -top cliffordwolf_freduce
+prep
+design -save gold
+proc; opt; freduce; opt
+write_verilog -noexpr -norename
+muxpack
+opt
+stat
+select -assert-count 0 t:$mux
+select -assert-count 1 t:$pmux
+design -stash gate
+design -import gold -as gold
+design -import gate -as gate
+miter -equiv -flatten -make_assert -make_outputs gold gate miter
+sat -verify -prove-asserts -show-ports miter