Merge pull request #48 from YosysHQ/placer_speedup

placer: low hanging speedups

4 files changed, 66 insertions, 32 deletions

diff --git a/common/placer1.cc b/common/placer1.cc
index 91320240..88f2fc47 100644
--- a/common/placer1.cc
+++ b/common/placer1.cc
@@ -70,6 +70,19 @@ class SAPlacer
             fast_bels.at(type_idx).at(loc.x).at(loc.y).push_back(bel);
         }
         diameter = std::max(max_x, max_y) + 1;
+
+        costs.resize(ctx->nets.size());
+        old_udata.reserve(ctx->nets.size());
+        decltype(NetInfo::udata) n = 0;
+        for (auto &net : ctx->nets) {
+            old_udata.emplace_back(net.second->udata);
+            net.second->udata = n++;
+        }
+    }
+
+    ~SAPlacer() {
+        for (auto &net : ctx->nets)
+            net.second->udata = old_udata[net.second->udata];
     }
 
     bool place()
@@ -149,7 +162,7 @@ class SAPlacer
         curr_tns = 0;
         for (auto &net : ctx->nets) {
             wirelen_t wl = get_net_metric(ctx, net.second.get(), MetricType::COST, curr_tns);
-            metrics[net.first] = wl;
+            costs[net.second->udata] = CostChange{wl, -1};
             curr_metric += wl;
         }
 
@@ -250,7 +263,7 @@ class SAPlacer
             curr_tns = 0;
             for (auto &net : ctx->nets) {
                 wirelen_t wl = get_net_metric(ctx, net.second.get(), MetricType::COST, curr_tns);
-                metrics[net.first] = wl;
+                costs[net.second->udata] = CostChange{wl, -1};
                 curr_metric += wl;
             }
 
@@ -339,10 +352,8 @@ class SAPlacer
     // Attempt a SA position swap, return true on success or false on failure
     bool try_swap_position(CellInfo *cell, BelId newBel)
     {
-        static std::unordered_set<NetInfo *> update;
-        static std::vector<std::pair<IdString, wirelen_t>> new_lengths;
-        new_lengths.clear();
-        update.clear();
+        static std::vector<NetInfo*> updates;
+        updates.clear();
         BelId oldBel = cell->bel;
         CellInfo *other_cell = ctx->getBoundBelCell(newBel);
         if (other_cell != nullptr && other_cell->belStrength > STRENGTH_WEAK) {
@@ -358,14 +369,23 @@ class SAPlacer
             ctx->unbindBel(newBel);
         }
 
-        for (const auto &port : cell->ports)
-            if (port.second.net != nullptr)
-                update.insert(port.second.net);
+        for (const auto &port : cell->ports) {
+            if (port.second.net != nullptr) {
+                auto &cost = costs[port.second.net->udata];
+                if (cost.new_cost == 0) continue;
+                cost.new_cost = 0;
+                updates.emplace_back(port.second.net);
+            }
+        }
 
         if (other_cell != nullptr) {
             for (const auto &port : other_cell->ports)
-                if (port.second.net != nullptr)
-                    update.insert(port.second.net);
+                if (port.second.net != nullptr) {
+                    auto &cost = costs[port.second.net->udata];
+                    if (cost.new_cost == 0) continue;
+                    cost.new_cost = 0;
+                    updates.emplace_back(port.second.net);
+                }
         }
 
         ctx->bindBel(newBel, cell, STRENGTH_WEAK);
@@ -383,12 +403,13 @@ class SAPlacer
         new_metric = curr_metric;
 
         // Recalculate metrics for all nets touched by the peturbation
-        for (auto net : update) {
-            new_metric -= metrics.at(net->name);
+        for (const auto &net : updates) {
+            auto &c = costs[net->udata];
+            new_metric -= c.curr_cost;
             float temp_tns = 0;
             wirelen_t net_new_wl = get_net_metric(ctx, net, MetricType::COST, temp_tns);
             new_metric += net_new_wl;
-            new_lengths.push_back(std::make_pair(net->name, net_new_wl));
+            c.new_cost = net_new_wl;
         }
 
         new_dist = get_constraints_distance(ctx, cell);
@@ -407,8 +428,10 @@ class SAPlacer
             goto swap_fail;
         }
         curr_metric = new_metric;
-        for (auto new_wl : new_lengths)
-            metrics.at(new_wl.first) = new_wl.second;
+        for (const auto &net : updates) {
+            auto &c = costs[net->udata];
+            c = CostChange{c.new_cost, -1};
+        }
 
         return true;
     swap_fail:
@@ -416,6 +439,8 @@ class SAPlacer
         if (other_cell != nullptr) {
             ctx->bindBel(newBel, other_cell, STRENGTH_WEAK);
         }
+        for (const auto &net : updates)
+            costs[net->udata].new_cost = -1;
         return false;
     }
 
@@ -444,7 +469,6 @@ class SAPlacer
     }
 
     Context *ctx;
-    std::unordered_map<IdString, wirelen_t> metrics;
     wirelen_t curr_metric = std::numeric_limits<wirelen_t>::max();
     float curr_tns = 0;
     float temp = 1000;
@@ -459,6 +483,13 @@ class SAPlacer
     const float post_legalise_temp = 10;
     const float post_legalise_dia_scale = 1.5;
     Placer1Cfg cfg;
+
+    struct CostChange {
+        wirelen_t curr_cost;
+        wirelen_t new_cost;
+    };
+    std::vector<CostChange> costs;
+    std::vector<decltype(NetInfo::udata)> old_udata;
 };
 
 bool placer1(Context *ctx, Placer1Cfg cfg)
diff --git a/ice40/arch.h b/ice40/arch.h
index 4c093ef9..8fd1af23 100644
--- a/ice40/arch.h
+++ b/ice40/arch.h
@@ -812,7 +812,7 @@ struct Arch : BaseCtx
     bool isBelLocationValid(BelId bel) const;
 
     // Helper function for above
-    bool logicCellsCompatible(const std::vector<const CellInfo *> &cells) const;
+    bool logicCellsCompatible(const CellInfo** it, const size_t size) const;
 
     // -------------------------------------------------
     // Assign architecure-specific arguments to nets and cells, which must be
diff --git a/ice40/arch_place.cc b/ice40/arch_place.cc
index bbddb7ee..c69fd34f 100644
--- a/ice40/arch_place.cc
+++ b/ice40/arch_place.cc
@@ -23,15 +23,17 @@
 #include "nextpnr.h"
 #include "util.h"
 
+#include <boost/range/iterator_range.hpp>
+
 NEXTPNR_NAMESPACE_BEGIN
 
-bool Arch::logicCellsCompatible(const std::vector<const CellInfo *> &cells) const
+bool Arch::logicCellsCompatible(const CellInfo** it, const size_t size) const
 {
     bool dffs_exist = false, dffs_neg = false;
     const NetInfo *cen = nullptr, *clk = nullptr, *sr = nullptr;
     int locals_count = 0;
 
-    for (auto cell : cells) {
+    for (auto cell : boost::make_iterator_range(it, it+size)) {
         NPNR_ASSERT(cell->belType == id_ICESTORM_LC);
         if (cell->lcInfo.dffEnable) {
             if (!dffs_exist) {
@@ -71,15 +73,15 @@ bool Arch::logicCellsCompatible(const std::vector<const CellInfo *> &cells) cons
 bool Arch::isBelLocationValid(BelId bel) const
 {
     if (getBelType(bel) == id_ICESTORM_LC) {
-        std::vector<const CellInfo *> bel_cells;
+        std::array<const CellInfo *, 8> bel_cells;
+        size_t num_cells = 0;
         Loc bel_loc = getBelLocation(bel);
         for (auto bel_other : getBelsByTile(bel_loc.x, bel_loc.y)) {
             CellInfo *ci_other = getBoundBelCell(bel_other);
-            if (ci_other != nullptr) {
-                bel_cells.push_back(ci_other);
-            }
+            if (ci_other != nullptr)
+                bel_cells[num_cells++] = ci_other;
         }
-        return logicCellsCompatible(bel_cells);
+        return logicCellsCompatible(bel_cells.data(), num_cells);
     } else {
         CellInfo *ci = getBoundBelCell(bel);
         if (ci == nullptr)
@@ -94,17 +96,18 @@ bool Arch::isValidBelForCell(CellInfo *cell, BelId bel) const
     if (cell->type == id_ICESTORM_LC) {
         NPNR_ASSERT(getBelType(bel) == id_ICESTORM_LC);
 
-        std::vector<const CellInfo *> bel_cells;
+        std::array<const CellInfo *, 8> bel_cells;
+        size_t num_cells = 0;
+
         Loc bel_loc = getBelLocation(bel);
         for (auto bel_other : getBelsByTile(bel_loc.x, bel_loc.y)) {
             CellInfo *ci_other = getBoundBelCell(bel_other);
-            if (ci_other != nullptr && bel_other != bel) {
-                bel_cells.push_back(ci_other);
-            }
+            if (ci_other != nullptr && bel_other != bel)
+                bel_cells[num_cells++] = ci_other;
         }
 
-        bel_cells.push_back(cell);
-        return logicCellsCompatible(bel_cells);
+        bel_cells[num_cells++] = cell;
+        return logicCellsCompatible(bel_cells.data(), num_cells);
     } else if (cell->type == id_SB_IO) {
         // Do not allow placement of input SB_IOs on blocks where there a PLL is outputting to.
 
diff --git a/ice40/chains.cc b/ice40/chains.cc
index 8638a96c..bb20b60b 100644
--- a/ice40/chains.cc
+++ b/ice40/chains.cc
@@ -97,7 +97,7 @@ class ChainConstrainer
             }
             tile.push_back(cell);
             chains.back().cells.push_back(cell);
-            bool split_chain = (!ctx->logicCellsCompatible(tile)) || (int(chains.back().cells.size()) > max_length);
+            bool split_chain = (!ctx->logicCellsCompatible(tile.data(), tile.size())) || (int(chains.back().cells.size()) > max_length);
             if (split_chain) {
                 CellInfo *passout = make_carry_pass_out(cell->ports.at(ctx->id("COUT")));
                 tile.pop_back();