From 28cf48e31f049f8343023de46cd916ac47fcfc5d Mon Sep 17 00:00:00 2001
From: Clifford Wolf <clifford@clifford.at>
Date: Thu, 14 Aug 2014 11:22:45 +0200
Subject: [PATCH] Some improvements in FSM mapping and recoding

---
 passes/fsm/fsm_map.cc    |  2 +-
 passes/fsm/fsm_recode.cc | 22 +++++++++++++++-------
 tests/fsm/generate.py    |  3 ++-
 3 files changed, 18 insertions(+), 9 deletions(-)

diff --git a/passes/fsm/fsm_map.cc b/passes/fsm/fsm_map.cc
index 048cf7e5f..60580eb46 100644
--- a/passes/fsm/fsm_map.cc
+++ b/passes/fsm/fsm_map.cc
@@ -285,7 +285,7 @@ static void map_fsm(RTLIL::Cell *fsm_cell, RTLIL::Module *module)
 				}
 			}
 
-			RTLIL::Cell *mux_cell = module->addCell(NEW_ID, "$safe_pmux");
+			RTLIL::Cell *mux_cell = module->addCell(NEW_ID, "$pmux");
 			mux_cell->setPort("\\A", sig_a);
 			mux_cell->setPort("\\B", sig_b);
 			mux_cell->setPort("\\S", sig_s);
diff --git a/passes/fsm/fsm_recode.cc b/passes/fsm/fsm_recode.cc
index 40fed130e..9c0da0a37 100644
--- a/passes/fsm/fsm_recode.cc
+++ b/passes/fsm/fsm_recode.cc
@@ -53,10 +53,10 @@ static void fsm_recode(RTLIL::Cell *cell, RTLIL::Module *module, FILE *fm_set_fs
 	std::string encoding = cell->attributes.count("\\fsm_encoding") ? cell->attributes.at("\\fsm_encoding").decode_string() : "auto";
 
 	log("Recoding FSM `%s' from module `%s' using `%s' encoding:\n", cell->name.c_str(), module->name.c_str(), encoding.c_str());
-	if (encoding != "none" && encoding != "one-hot" && encoding != "binary") {
-		if (encoding != "auto")
-			log("  unkown encoding `%s': using auto (%s) instead.\n", encoding.c_str(), default_encoding.c_str());
-		encoding = default_encoding;
+
+	if (encoding != "none" && encoding != "one-hot" && encoding != "binary" && encoding != "auto") {
+		log("  unkown encoding `%s': using auto instead.\n", encoding.c_str());
+		encoding = "auto";
 	}
 
 	if (encoding == "none") {
@@ -70,10 +70,18 @@ static void fsm_recode(RTLIL::Cell *cell, RTLIL::Module *module, FILE *fm_set_fs
 	if (fm_set_fsm_file != NULL)
 		fm_set_fsm_print(cell, module, fsm_data, "r", fm_set_fsm_file);
 
+	if (encoding == "auto") {
+		if (!default_encoding.empty())
+			encoding = default_encoding;
+		else
+			encoding = SIZE(fsm_data.state_table) < 32 ? "one-hot" : "binary";
+		log("  mapping auto encoding to `%s` for this FSM.\n", encoding.c_str());
+	}
+
 	if (encoding == "one-hot") {
 		fsm_data.state_bits = fsm_data.state_table.size();
 	} else
-	if (encoding == "auto" || encoding == "binary") {
+	if (encoding == "binary") {
 		fsm_data.state_bits = ceil(log2(fsm_data.state_table.size()));
 	} else
 		log_error("FSM encoding `%s' is not supported!\n", encoding.c_str());
@@ -88,7 +96,7 @@ static void fsm_recode(RTLIL::Cell *cell, RTLIL::Module *module, FILE *fm_set_fs
 			new_code = RTLIL::Const(RTLIL::State::Sa, fsm_data.state_bits);
 			new_code.bits[state_idx] = RTLIL::State::S1;
 		} else
-		if (encoding == "auto" || encoding == "binary") {
+		if (encoding == "binary") {
 			new_code = RTLIL::Const(state_idx, fsm_data.state_bits);
 		} else
 			log_abort();
@@ -124,7 +132,7 @@ struct FsmRecodePass : public Pass {
 	virtual void execute(std::vector<std::string> args, RTLIL::Design *design)
 	{
 		FILE *fm_set_fsm_file = NULL;
-		std::string default_encoding = "one-hot";
+		std::string default_encoding;
 
 		log_header("Executing FSM_RECODE pass (re-assigning FSM state encoding).\n");
 		size_t argidx;
diff --git a/tests/fsm/generate.py b/tests/fsm/generate.py
index 66ca2af5e..b5b4626df 100644
--- a/tests/fsm/generate.py
+++ b/tests/fsm/generate.py
@@ -52,7 +52,8 @@ for idx in range(50):
         print('  output reg%s [%d:0] y;' % (random.choice(['', ' signed']), random.randint(0, 31)))
         print('  output reg%s [%d:0] z;' % (random.choice(['', ' signed']), random.randint(0, 31)))
         state_bits = random.randint(5, 16);
-        print('  reg [%d:0] state;' % (state_bits-1))
+        print('  %sreg [%d:0] state;' % (random.choice(['', '(* fsm_encoding = "one-hot" *)',
+                '(* fsm_encoding = "binary" *)']), state_bits-1))
         states=[]
         for i in range(random.randint(2, 10)):
             n = random.randint(0, 2**state_bits-1)
-- 
2.30.2