Allow write_lakeroad backend to write output to file instead of std…

…out. (#9)

* Add code to write_lakeroad to file instead of stdout

* Fix a bug for writing to stdout as well

* Add suggested code

backends/lakeroad/example.ys

@@ -4,4 +4,8 @@ module test(input [1:0] a, input b, output o);
 endmodule
 EOF
 
-write_lakeroad
+# Write output to stdout
+write_lakeroad
+# Write output to file.egg
+write_lakeroad file.egg
+!rm file.egg

backends/lakeroad/lakeroad.cc

@@ -25,8 +25,8 @@
 #include "kernel/rtlil.h"
 #include "kernel/sigtools.h"
 #include "kernel/yw.h"
-#include <string>
 #include <assert.h>
+#include <string>
 
 USING_YOSYS_NAMESPACE
 PRIVATE_NAMESPACE_BEGIN
@@ -1714,11 +1714,22 @@ struct BtorBackend : public Backend {
 	void execute(std::ostream *&f, std::string filename, std::vector<std::string> args, RTLIL::Design *design) override
 	{
 		log_header(design, "Executing Lakeroad egglog backend.\n");
-
 		RTLIL::Module *topmod = design->top_module();
 
+		// Copied from firrtl code.
+		size_t argidx = args.size();
+
+		if (filename == "") {
+			// The command itself is given as an arg
+			if (argidx > 1 && args[argidx - 1][0] != '-') {
+				// extra_args and friends need to see this argument.
+				argidx -= 1;
+				filename = args[argidx];
+			}
+		}
+
 		// Has to come after other arg parsing.
-		extra_args(f, filename, args, args.size());
+		extra_args(f, filename, args, argidx);
 
 		if (topmod == nullptr)
 			log_cmd_error("No top module found.\n");