cxxrtl: get rid of -O5 aka `opt_clean -purge` optimization level.

This isn't actually necessary anymore after scheduling was improved,
and `clean -purge` disrupts the mapping between wires in the input
RTLIL netlist and the output CXXRTL code.

diff --git a/backends/cxxrtl/cxxrtl.cc b/backends/cxxrtl/cxxrtl.cc
index f3ed3f6232542807ff920cfc3e4a4d1590900556..549404184420f0875adc0936d6d7421398e85c62 100644 (file)
--- a/backends/cxxrtl/cxxrtl.cc
+++ b/backends/cxxrtl/cxxrtl.cc
@@ -2306,10 +2306,7 @@ struct CxxrtlBackend : public Backend {
                log("        like -O3, and localize public wires not marked (*keep*) if possible.\n");
                log("\n");
                log("    -O5\n");
-               log("        like -O4, and run `opt_clean -purge` first.\n");
-               log("\n");
-               log("    -O6\n");
-               log("        like -O5, and run `proc; flatten` first.\n");
+               log("        like -O4, and run `proc; flatten` first.\n");
                log("\n");
        }
        void execute(std::ostream *&f, std::string filename, std::vector<std::string> args, RTLIL::Design *design) YS_OVERRIDE
@@ -2343,13 +2340,10 @@ struct CxxrtlBackend : public Backend {
                extra_args(f, filename, args, argidx);
 
                switch (opt_level) {
-                       case 6:
+                       case 5:
                                worker.max_opt_level = true;
                                worker.run_proc_flatten = true;
                                YS_FALLTHROUGH
-                       case 5:
-                               worker.run_opt_clean_purge = true;
-                               YS_FALLTHROUGH
                        case 4:
                                worker.localize_public = true;
                                YS_FALLTHROUGH