shiftx2mux: fix select out of bounds

tests/techmap/run-test.sh

@@ -6,7 +6,7 @@ for x in *.ys; do
 	echo "all:: run-$x"
 	echo "run-$x:"
 	echo "	@echo 'Running $x..'"
-	echo "	@../../yosys -ql ${x%.ys}.log $x"
+	echo "	@../../yosys -ql ${x%.ys}.log -e 'select out of bounds' $x"
 done
 for s in *.sh; do
 	if [ "$s" != "run-test.sh" ]; then

tests/techmap/shiftx2mux.ys

@@ -108,3 +108,14 @@ design -import gate -as gate
 miter -equiv -flatten -make_assert -make_outputs gold gate miter
 sat -verify -prove-asserts -show-ports miter
 
+
+design -reset
+read_verilog <<EOT
+module top(input [6:0] A, input [1:0] B, output [1:0] Y);
+wire [7:0] AA = {1'bx, A};
+assign Y = AA[B*2 +: 2];
+endmodule
+EOT
+opt
+wreduce
+equiv_opt techmap