Add error check for duplicate pin location side specifications

Cases such as:

    <pinlocations pattern="custom">
      <loc side="left">clb.I clb.clk</loc>
      <loc side="left">clb.O</loc>
    </pinlocations>

are now treated as illegal, since pins are specified multiple times for
the 'left' side. Previously the last of the matching specifications
would overwrite the earlier specifications.

The correct format would be:

    <pinlocations pattern="custom">
      <loc side="left">clb.O clb.I clb.clk</loc>
    </pinlocations>

Author: kmurray

libarchfpga/src/read_xml_arch_file.cpp

@@ -365,6 +365,7 @@ static void SetupPinLocationsAndPinClasses(pugi::xml_node Locations,
 	/* Load the pin locations */
 	if (Type->pin_location_distribution == E_CUSTOM_PIN_DISTR) {
 		Cur = Locations.first_child();
+        std::set<e_side> seen_sides;
 		while (Cur) {
 			check_node(Cur, "loc", loc_data);
 
@@ -377,7 +378,7 @@ static void SetupPinLocationsAndPinClasses(pugi::xml_node Locations,
 			}
 
 			/* Get side */
-			int side = 0;
+			e_side side;
 			Prop = get_attribute(Cur, "side", loc_data).value();
 			if (0 == strcmp(Prop, "left")) {
 				side = LEFT;
@@ -392,6 +393,14 @@ static void SetupPinLocationsAndPinClasses(pugi::xml_node Locations,
 						"'%s' is not a valid side.\n", Prop);
 			}
 
+            //Check for duplicate side specifications, since the code below silently overwrites if there are duplicates
+            if (seen_sides.count(side)) {
+				archfpga_throw(loc_data.filename_c_str(), loc_data.line(Cur),
+						"Duplicate pin location side specification. Only a single <loc> per side is permitted.\n");
+            } else {
+                seen_sides.insert(side);
+            }
+
 			/* Check location is on perimeter */
 			if ((TOP == side) && (height != (Type->height - 1))) {
 				archfpga_throw(loc_data.filename_c_str(), loc_data.line(Cur),
@@ -408,12 +417,10 @@ static void SetupPinLocationsAndPinClasses(pugi::xml_node Locations,
 			Count = Tokens.size();
 			Type->num_pin_loc_assignments[0][height][side] = Count;
 			if (Count > 0) {
-				Type->pin_loc_assignments[0][height][side] = (char**) vtr::calloc(
-						Count, sizeof(char*));
+				Type->pin_loc_assignments[0][height][side] = (char**) vtr::calloc(Count, sizeof(char*));
 				for (int pin = 0; pin < Count; ++pin) {
 					/* Store location assignment */
-					Type->pin_loc_assignments[0][height][side][pin] = vtr::strdup(
-							Tokens[pin].c_str());
+					Type->pin_loc_assignments[0][height][side][pin] = vtr::strdup(Tokens[pin].c_str());
 
 					/* Advance through list of pins in this location */
 				}