Do not optimize away FFs in "prep" and Verific fron-end

Signed-off-by: Claire Wolf <claire@symbioticeda.com>

3 files changed, 17 insertions, 7 deletions

diff --git a/frontends/verific/verific.cc b/frontends/verific/verific.cc
index cb0368fd5..a753ca289 100644
--- a/frontends/verific/verific.cc
+++ b/frontends/verific/verific.cc
@@ -2175,6 +2175,9 @@ struct VerificPass : public Pass {
 			RuntimeFlags::SetVar("vhdl_support_variable_slice", 1);
 			RuntimeFlags::SetVar("vhdl_ignore_assertion_statements", 0);
 
+			RuntimeFlags::SetVar("veri_preserve_assignments", 1);
+			RuntimeFlags::SetVar("vhdl_preserve_assignments", 1);
+
 			// Workaround for VIPER #13851
 			RuntimeFlags::SetVar("veri_create_name_for_unnamed_gen_block", 1);
 
diff --git a/passes/opt/opt.cc b/passes/opt/opt.cc
index 396819883..b852e6ae8 100644
--- a/passes/opt/opt.cc
+++ b/passes/opt/opt.cc
@@ -44,8 +44,8 @@ struct OptPass : public Pass {
 		log("        opt_muxtree\n");
 		log("        opt_reduce [-fine] [-full]\n");
 		log("        opt_merge [-share_all]\n");
-		log("        opt_share (-full only)\n");
-		log("        opt_rmdff [-keepdc] [-sat]\n");
+		log("        opt_share  (-full only)\n");
+		log("        opt_rmdff [-keepdc] [-sat]  (except when called with -noff)\n");
 		log("        opt_clean [-purge]\n");
 		log("        opt_expr [-mux_undef] [-mux_bool] [-undriven] [-clkinv] [-fine] [-full] [-keepdc]\n");
 		log("    while <changed design>\n");
@@ -55,7 +55,7 @@ struct OptPass : public Pass {
 		log("    do\n");
 		log("        opt_expr [-mux_undef] [-mux_bool] [-undriven] [-clkinv] [-fine] [-full] [-keepdc]\n");
 		log("        opt_merge [-share_all]\n");
-		log("        opt_rmdff [-keepdc] [-sat]\n");
+		log("        opt_rmdff [-keepdc] [-sat]  (except when called with -noff)\n");
 		log("        opt_clean [-purge]\n");
 		log("    while <changed design in opt_rmdff>\n");
 		log("\n");
@@ -73,6 +73,7 @@ struct OptPass : public Pass {
 		std::string opt_rmdff_args;
 		bool opt_share = false;
 		bool fast_mode = false;
+		bool noff_mode = false;
 
 		log_header(design, "Executing OPT pass (performing simple optimizations).\n");
 		log_push();
@@ -127,6 +128,10 @@ struct OptPass : public Pass {
 				fast_mode = true;
 				continue;
 			}
+			if (args[argidx] == "-noff") {
+				noff_mode = true;
+				continue;
+			}
 			break;
 		}
 		extra_args(args, argidx, design);
@@ -137,7 +142,8 @@ struct OptPass : public Pass {
 				Pass::call(design, "opt_expr" + opt_expr_args);
 				Pass::call(design, "opt_merge" + opt_merge_args);
 				design->scratchpad_unset("opt.did_something");
-				Pass::call(design, "opt_rmdff" + opt_rmdff_args);
+				if (!noff_mode)
+					Pass::call(design, "opt_rmdff" + opt_rmdff_args);
 				if (design->scratchpad_get_bool("opt.did_something") == false)
 					break;
 				Pass::call(design, "opt_clean" + opt_clean_args);
@@ -156,7 +162,8 @@ struct OptPass : public Pass {
 				Pass::call(design, "opt_merge" + opt_merge_args);
 				if (opt_share)
 					Pass::call(design, "opt_share");
-				Pass::call(design, "opt_rmdff" + opt_rmdff_args);
+				if (!noff_mode)
+					Pass::call(design, "opt_rmdff" + opt_rmdff_args);
 				Pass::call(design, "opt_clean" + opt_clean_args);
 				Pass::call(design, "opt_expr" + opt_expr_args);
 				if (design->scratchpad_get_bool("opt.did_something") == false)
diff --git a/techlibs/common/prep.cc b/techlibs/common/prep.cc
index cdd21c3b3..82e6126c6 100644
--- a/techlibs/common/prep.cc
+++ b/techlibs/common/prep.cc
@@ -192,7 +192,7 @@ struct PrepPass : public ScriptPass
 			run(nokeepdc ? "opt_expr" : "opt_expr -keepdc");
 			run("opt_clean");
 			run("check");
-			run(nokeepdc ? "opt" : "opt -keepdc");
+			run(nokeepdc ? "opt -noff" : "opt -noff -keepdc");
 			if (!ifxmode) {
 				if (help_mode)
 					run("wreduce -keepdc [-memx]");
@@ -208,7 +208,7 @@ struct PrepPass : public ScriptPass
 				run("opt_clean");
 				run("memory_collect");
 			}
-			run(nokeepdc ? "opt -fast" : "opt -keepdc -fast");
+			run(nokeepdc ? "opt -noff -fast" : "opt -noff -keepdc -fast");
 		}
 
 		if (check_label("check"))