place_sa: Add a rip-up feature when initial placement fails

Signed-off-by: David Shah <davey1576@gmail.com>

common/place_sa.cc

@@ -72,33 +72,58 @@ static int random_int_between(rnd_state &rnd, int a, int b)
 // Initial random placement
 static void place_initial(Design *design, CellInfo *cell, rnd_state &rnd)
 {
+    bool all_placed = false;
+    int iters = 25;
+    while(!all_placed) {
         BelId best_bel = BelId();
-    float best_score = std::numeric_limits<float>::infinity();
+        float best_score = std::numeric_limits<float>::infinity(), best_ripup_score = std::numeric_limits<float>::infinity();
         Chip &chip = design->chip;
+        CellInfo *ripup_target = nullptr;
+        BelId ripup_bel = BelId();
         if (cell->bel != BelId()) {
             chip.unbindBel(cell->bel);
             cell->bel = BelId();
         }
         BelType targetType = belTypeFromId(cell->type);
         for (auto bel : chip.getBels()) {
-        if (chip.getBelType(bel) == targetType && chip.checkBelAvail(bel) &&
+            if (chip.getBelType(bel) == targetType && isValidBelForCell(design, cell, bel)) {
-            isValidBelForCell(design, cell, bel)) {
+                if (chip.checkBelAvail(bel)) {
                     float score = random_float_upto(rnd, 1.0);
                     if (score <= best_score) {
                         best_score = score;
                         best_bel = bel;
                     }
+                } else {
+                    float score = random_float_upto(rnd, 1.0);
+                    if (score <= best_ripup_score) {
+                        best_ripup_score = score;
+                        ripup_target = design->cells.at(chip.getBelCell(bel, true));
+                        ripup_bel = bel;
+                    }
+
+                }
+
             }
         }
         if (best_bel == BelId()) {
+            if (iters == 0 || ripup_bel == BelId())
                 log_error("failed to place cell '%s' of type '%s'\n",
                       cell->name.c_str(), cell->type.c_str());
+            --iters;
+            chip.unbindBel(ripup_target->bel);
+            ripup_target->bel = BelId();
+            best_bel = ripup_bel;
+        } else {
+            all_placed = true;
         }
         cell->bel = best_bel;
         chip.bindBel(cell->bel, cell->name);
 
         // Back annotate location
         cell->attrs["BEL"] = chip.getBelName(cell->bel).str();
+        cell = ripup_target;
+    }
+
 }
 
 // Stores the state of the SA placer

ice40/arch_place.cc

@@ -38,7 +38,8 @@ static bool logicCellsCompatible(const std::vector<const CellInfo *> &cells)
 {
     bool dffs_exist = false, dffs_neg = false;
     const NetInfo *cen = nullptr, *clk = nullptr, *sr = nullptr;
-    std::unordered_set<const NetInfo *> locals;
+    static std::unordered_set<const NetInfo *> locals;
+    locals.clear();
 
     for (auto cell : cells) {
         if (bool_or_default(cell->params, "DFF_ENABLE")) {

ice40/pack.cc

@@ -279,7 +279,9 @@ static void pack_io(Design *design)
 static void insert_global(Design *design, NetInfo *net, bool is_reset,
                           bool is_cen)
 {
-    CellInfo *gb = create_ice_cell(design, "SB_GB");
+    std::string glb_name = net->name.str() + std::string("_$glb_") +
+                          (is_reset ? "sr" : (is_cen ? "ce" : "clk"));
+    CellInfo *gb = create_ice_cell(design, "SB_GB", "$gbuf_" + glb_name);
     gb->ports["USER_SIGNAL_TO_GLOBAL_BUFFER"].net = net;
     PortRef pr;
     pr.cell = gb;
@@ -289,8 +291,7 @@ static void insert_global(Design *design, NetInfo *net, bool is_reset,
     pr.cell = gb;
     pr.port = "GLOBAL_BUFFER_OUTPUT";
     NetInfo *glbnet = new NetInfo();
-    glbnet->name = net->name.str() + std::string("_glb_") +
+    glbnet->name = glb_name;
-                   (is_reset ? "sr" : (is_cen ? "ce" : "clk"));
     glbnet->driver = pr;
     design->nets[glbnet->name] = glbnet;
     gb->ports["GLOBAL_BUFFER_OUTPUT"].net = glbnet;
@@ -363,19 +364,22 @@ static void promote_globals(Design *design)
             ++prom_resets;
             clock_count.erase(rstnet->name);
             reset_count.erase(rstnet->name);
-
+            cen_count.erase(rstnet->name);
         } else if (global_cen->second > global_clock->second && prom_cens < 4) {
             NetInfo *cennet = design->nets[global_cen->first];
             insert_global(design, cennet, false, true);
             ++prom_globals;
             ++prom_cens;
-            cen_count.erase(cennet->name);
             clock_count.erase(cennet->name);
+            reset_count.erase(cennet->name);
+            cen_count.erase(cennet->name);
         } else if (global_clock->second != 0) {
             NetInfo *clknet = design->nets[global_clock->first];
             insert_global(design, clknet, false, false);
             ++prom_globals;
             clock_count.erase(clknet->name);
+            reset_count.erase(clknet->name);
+            cen_count.erase(clknet->name);
         } else {
             break;
         }