Prefer noninverting FFs in dfflibmap

diff --git a/passes/techmap/dfflibmap.cc b/passes/techmap/dfflibmap.cc
index 4d7a1a7045be53e6746c7d80103d5133a00a6267..3195e5a786735d888a3adac977316d547736ce90 100644 (file)
--- a/passes/techmap/dfflibmap.cc
+++ b/passes/techmap/dfflibmap.cc
@@ -108,6 +108,7 @@ static void find_cell(LibertyAst *ast, std::string cell_type, bool clkpol, bool
        LibertyAst *best_cell = NULL;
        std::map<std::string, char> best_cell_ports;
        int best_cell_pins = 0;
+       bool best_cell_noninv = false;
        double best_cell_area = 0;
 
        if (ast->id != "library")
@@ -155,6 +156,7 @@ static void find_cell(LibertyAst *ast, std::string cell_type, bool clkpol, bool
 
                int num_pins = 0;
                bool found_output = false;
+               bool found_noninv_output = false;
                for (auto pin : cell->children)
                {
                        if (pin->id != "pin" || pin->args.size() != 1)
@@ -175,10 +177,14 @@ static void find_cell(LibertyAst *ast, std::string cell_type, bool clkpol, bool
                                        value.erase(pos, 1);
                                if (value == ff->args[0]) {
                                        this_cell_ports[pin->args[0]] = cell_next_pol ? 'Q' : 'q';
+                                       if (cell_next_pol)
+                                               found_noninv_output = true;
                                        found_output = true;
                                } else
                                if (value == ff->args[1]) {
                                        this_cell_ports[pin->args[0]] = cell_next_pol ? 'q' : 'Q';
+                                       if (!cell_next_pol)
+                                               found_noninv_output = true;
                                        found_output = true;
                                }
                        }
@@ -187,7 +193,7 @@ static void find_cell(LibertyAst *ast, std::string cell_type, bool clkpol, bool
                                this_cell_ports[pin->args[0]] = 0;
                }
 
-               if (!found_output || (best_cell != NULL && num_pins > best_cell_pins))
+               if (!found_output || (best_cell != NULL && (num_pins > best_cell_pins || (best_cell_noninv && !found_noninv_output))))
                        continue;
 
                if (best_cell != NULL && num_pins == best_cell_pins && area > best_cell_area)
@@ -196,12 +202,14 @@ static void find_cell(LibertyAst *ast, std::string cell_type, bool clkpol, bool
                best_cell = cell;
                best_cell_pins = num_pins;
                best_cell_area = area;
+               best_cell_noninv = found_noninv_output;
                best_cell_ports.swap(this_cell_ports);
        continue_cell_loop:;
        }
 
        if (best_cell != NULL) {
-               log("  cell %s (pins=%d, area=%.2f) is a direct match for cell type %s.\n", best_cell->args[0].c_str(), best_cell_pins, best_cell_area, cell_type.c_str());
+               log("  cell %s (%sinv, pins=%d, area=%.2f) is a direct match for cell type %s.\n",
+                               best_cell->args[0].c_str(), best_cell_noninv ? "non" : "", best_cell_pins, best_cell_area, cell_type.c_str());
                if (prepare_mode) {
                        cell_mappings[cell_type].cell_name = cell_type;
                        cell_mappings[cell_type].ports["C"] = 'C';
@@ -221,6 +229,7 @@ static void find_cell_sr(LibertyAst *ast, std::string cell_type, bool clkpol, bo
        LibertyAst *best_cell = NULL;
        std::map<std::string, char> best_cell_ports;
        int best_cell_pins = 0;
+       bool best_cell_noninv = false;
        double best_cell_area = 0;
 
        if (ast->id != "library")
@@ -260,6 +269,7 @@ static void find_cell_sr(LibertyAst *ast, std::string cell_type, bool clkpol, bo
 
                int num_pins = 0;
                bool found_output = false;
+               bool found_noninv_output = false;
                for (auto pin : cell->children)
                {
                        if (pin->id != "pin" || pin->args.size() != 1)
@@ -280,10 +290,14 @@ static void find_cell_sr(LibertyAst *ast, std::string cell_type, bool clkpol, bo
                                        value.erase(pos, 1);
                                if (value == ff->args[0]) {
                                        this_cell_ports[pin->args[0]] = cell_next_pol ? 'Q' : 'q';
+                                       if (cell_next_pol)
+                                               found_noninv_output = true;
                                        found_output = true;
                                } else
                                if (value == ff->args[1]) {
                                        this_cell_ports[pin->args[0]] = cell_next_pol ? 'q' : 'Q';
+                                       if (!cell_next_pol)
+                                               found_noninv_output = true;
                                        found_output = true;
                                }
                        }
@@ -292,7 +306,7 @@ static void find_cell_sr(LibertyAst *ast, std::string cell_type, bool clkpol, bo
                                this_cell_ports[pin->args[0]] = 0;
                }
 
-               if (!found_output || (best_cell != NULL && num_pins > best_cell_pins))
+               if (!found_output || (best_cell != NULL && (num_pins > best_cell_pins || (best_cell_noninv && !found_noninv_output))))
                        continue;
 
                if (best_cell != NULL && num_pins == best_cell_pins && area > best_cell_area)
@@ -301,12 +315,14 @@ static void find_cell_sr(LibertyAst *ast, std::string cell_type, bool clkpol, bo
                best_cell = cell;
                best_cell_pins = num_pins;
                best_cell_area = area;
+               best_cell_noninv = found_noninv_output;
                best_cell_ports.swap(this_cell_ports);
        continue_cell_loop:;
        }
 
        if (best_cell != NULL) {
-               log("  cell %s (pins=%d, area=%.2f) is a direct match for cell type %s.\n", best_cell->args[0].c_str(), best_cell_pins, best_cell_area, cell_type.c_str());
+               log("  cell %s (%sinv, pins=%d, area=%.2f) is a direct match for cell type %s.\n",
+                               best_cell->args[0].c_str(), best_cell_noninv ? "non" : "", best_cell_pins, best_cell_area, cell_type.c_str());
                if (prepare_mode) {
                        cell_mappings[cell_type].cell_name = cell_type;
                        cell_mappings[cell_type].ports["C"] = 'C';