Add regression test for negative packed array bounds

Check that variable selects of a packed array with negative bounds use the
correct index width and can read back assigned elements.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>

ivtest/ivltests/sv_partsel_var_negative_packed.v

@@ -0,0 +1,33 @@
+// Check variable selects of packed arrays with negative bounds.
+
+module test;
+
+  reg failed;
+  reg [-8:-1][3:0] a;
+  reg signed [2:0] i;
+
+  `define check(val, exp) \
+    if (val !== exp) begin \
+      $display("FAILED(%0d). '%s' expected %b, got %b", `__LINE__, \
+               `"val`", exp, val); \
+      failed = 1'b1; \
+    end
+
+  initial begin
+    failed = 1'b0;
+    a = '0;
+
+    i = -1;
+    a[i] = 4'ha;
+    i = -2;
+    a[i] = 4'h5;
+
+    `check(a[-1], 4'ha);
+    `check(a[-2], 4'h5);
+
+    if (!failed) begin
+      $display("PASSED");
+    end
+  end
+
+endmodule

ivtest/regress-vvp.list

@@ -352,6 +352,7 @@ sv_net_decl_assign		vvp_tests/sv_net_decl_assign.json
 sv_package_lifetime		vvp_tests/sv_package_lifetime.json
 sv_package_lifetime_fail	vvp_tests/sv_package_lifetime_fail.json
 sv_parameter_type		vvp_tests/sv_parameter_type.json
+sv_partsel_var_negative_packed	vvp_tests/sv_partsel_var_negative_packed.json
 sv_queue_ap_method		vvp_tests/sv_queue_ap_method.json
 sv_queue_assign_op		vvp_tests/sv_queue_assign_op.json
 sv_queue_method_insert_too_few_arg_fail	vvp_tests/sv_queue_method_insert_too_few_arg_fail.json

ivtest/vvp_tests/sv_partsel_var_negative_packed.json

@@ -0,0 +1,8 @@
+{
+    "type"          : "normal",
+    "source"        : "sv_partsel_var_negative_packed.v",
+    "iverilog-args" : [ "-g2005-sv" ],
+    "vlog95" : {
+        "iverilog-args" : [ "-pallowsigned=1" ]
+    }
+}