ice40: Proper global promotion

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

1 files changed, 57 insertions, 22 deletions

diff --git a/ice40/pack.cc b/ice40/pack.cc
index d88870e0..dde8ed57 100644
--- a/ice40/pack.cc
+++ b/ice40/pack.cc
@@ -289,13 +289,15 @@ 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() + "_glb";
+    glbnet->name = net->name.str() + std::string("_glb_") +
+                   (is_reset ? "sr" : (is_cen ? "ce" : "clk"));
     glbnet->driver = pr;
     design->nets[glbnet->name] = glbnet;
     gb->ports["GLOBAL_BUFFER_OUTPUT"].net = glbnet;
     std::vector<PortRef> keep_users;
     for (auto user : net->users) {
-        if (is_clock_port(user) || (is_reset && is_reset_port(user))) {
+        if (is_clock_port(user) || (is_reset && is_reset_port(user)) ||
+            (is_cen && is_enable_port(user))) {
             user.cell->ports[user.port].net = glbnet;
             glbnet->users.push_back(user);
         } else {
@@ -311,39 +313,72 @@ static void promote_globals(Design *design)
 {
     log_info("Promoting globals..\n");
 
-    std::unordered_map<IdString, int> clock_count;
-    std::unordered_map<IdString, int> reset_count;
-
+    std::unordered_map<IdString, int> clock_count, reset_count, cen_count;
     for (auto net : design->nets) {
         NetInfo *ni = net.second;
         if (ni->driver.cell != nullptr && !is_global_net(ni)) {
             clock_count[net.first] = 0;
             reset_count[net.first] = 0;
+            cen_count[net.first] = 0;
+
             for (auto user : ni->users) {
                 if (is_clock_port(user))
                     clock_count[net.first]++;
                 if (is_reset_port(user))
                     reset_count[net.first]++;
+                if (is_enable_port(user))
+                    cen_count[net.first]++;
             }
         }
     }
-    auto global_clock = std::max_element(clock_count.begin(), clock_count.end(),
-                                         [](const std::pair<IdString, int> &a,
-                                            const std::pair<IdString, int> &b) {
-                                             return a.second < b.second;
-                                         });
-    if (global_clock->second > 0) {
-        NetInfo *clknet = design->nets[global_clock->first];
-        insert_global(design, clknet, false, false);
-    }
-    auto global_reset = std::max_element(reset_count.begin(), reset_count.end(),
-                                         [](const std::pair<IdString, int> &a,
-                                            const std::pair<IdString, int> &b) {
-                                             return a.second < b.second;
-                                         });
-    if (global_reset->second > 0) {
-        NetInfo *rstnet = design->nets[global_reset->first];
-        insert_global(design, rstnet, true, false);
+    int prom_globals = 0, prom_resets = 0, prom_cens = 0;
+    int gbs_available = 8;
+    for (auto cell : design->cells)
+        if (is_gbuf(cell.second))
+            --gbs_available;
+    while (prom_globals < gbs_available) {
+        auto global_clock =
+                std::max_element(clock_count.begin(), clock_count.end(),
+                                 [](const std::pair<IdString, int> &a,
+                                    const std::pair<IdString, int> &b) {
+                                     return a.second < b.second;
+                                 });
+
+        auto global_reset =
+                std::max_element(reset_count.begin(), reset_count.end(),
+                                 [](const std::pair<IdString, int> &a,
+                                    const std::pair<IdString, int> &b) {
+                                     return a.second < b.second;
+                                 });
+        auto global_cen =
+                std::max_element(cen_count.begin(), cen_count.end(),
+                                 [](const std::pair<IdString, int> &a,
+                                    const std::pair<IdString, int> &b) {
+                                     return a.second < b.second;
+                                 });
+        if (global_reset->second > global_clock->second && prom_resets < 4) {
+            NetInfo *rstnet = design->nets[global_reset->first];
+            insert_global(design, rstnet, true, false);
+            ++prom_globals;
+            ++prom_resets;
+            clock_count.erase(rstnet->name);
+            reset_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);
+        } 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);
+        } else {
+            break;
+        }
     }
 }