From 3ef45d2a27416ee14239dde6a69b43c870ea07b7 Mon Sep 17 00:00:00 2001
From: David Shah <davey1576@gmail.com>
Date: Wed, 13 Jun 2018 19:10:12 +0200
Subject: Another heuristic experiment

Signed-off-by: David Shah <davey1576@gmail.com>
---
 common/place.cc | 95 +++++++++++----------------------------------------------
 1 file changed, 18 insertions(+), 77 deletions(-)

(limited to 'common/place.cc')

diff --git a/common/place.cc b/common/place.cc
index fbb74395..d28d7ce9 100644
--- a/common/place.cc
+++ b/common/place.cc
@@ -123,45 +123,32 @@ void place_design(Design *design)
     }
 }
 
-static void place_cell(Design *design, CellInfo *cell, BelId closeTo,
-                       size_t &placed_cells,
-                       std::queue<CellInfo *> &visit_cells)
+static void place_cell(Design *design, CellInfo *cell)
 {
     assert(cell->bel == BelId());
     float best_distance = std::numeric_limits<float>::infinity();
     BelId best_bel = BelId();
     Chip &chip = design->chip;
     BelType targetType = belTypeFromId(cell->type);
-    PosInfo origin;
-    if (closeTo != BelId()) {
-        origin = chip.getBelPosition(closeTo);
-        for (auto bel : chip.getBelsAtSameTile(closeTo)) {
-            if (chip.getBelType(bel) == targetType && chip.checkBelAvail(bel) &&
-                isValidBelForCell(design, cell, bel)) {
-                // prefer same tile
-                best_bel = bel;
-                goto placed;
-            }
-        }
-    }
     for (auto bel : chip.getBels()) {
         if (chip.getBelType(bel) == targetType && chip.checkBelAvail(bel) &&
             isValidBelForCell(design, cell, bel)) {
-            if (closeTo == BelId()) {
-                best_distance = 0;
-                best_bel = bel;
-                goto placed;
-            } else {
-                float distance =
-                        chip.estimateDelay(origin, chip.getBelPosition(bel));
-                if (distance < best_distance) {
-                    best_distance = distance;
-                    best_bel = bel;
+            float distance = 0;
+            PosInfo belPosition = chip.getBelPosition(bel);
+            for (auto port : cell->ports) {
+                const PortInfo &pi = port.second;
+                if(pi.net != nullptr && pi.type == PORT_IN) {
+                    CellInfo *drv = pi.net->driver.cell;
+                    if (drv != nullptr && drv->bel != BelId())
+                        distance += chip.estimateDelay(chip.getBelPosition(drv->bel), belPosition);
                 }
             }
+            if (distance < best_distance) {
+                best_distance = distance;
+                best_bel = bel;
+            }
         }
     }
-placed:
     if (best_bel == BelId()) {
         log_error("failed to place cell '%s' of type '%s'\n",
                   cell->name.c_str(), cell->type.c_str());
@@ -171,42 +158,6 @@ placed:
 
     // Back annotate location
     cell->attrs["BEL"] = chip.getBelName(cell->bel).str();
-    placed_cells++;
-    visit_cells.push(cell);
-}
-
-static void place_cell_neighbours(Design *design, CellInfo *cell,
-                                  size_t &placed_cells,
-                                  std::queue<CellInfo *> &visit_cells)
-{
-    if (cell->bel == BelId())
-        return;
-    int placed_count = 0;
-    const int count_thresh = 15;
-    for (auto port : cell->ports) {
-        NetInfo *net = port.second.net;
-        if (net != nullptr) {
-            for (auto user : net->users) {
-                if (net->users.size() > 3)
-                    continue;
-                if (user.cell != nullptr && user.cell->bel == BelId()) {
-                    place_cell(design, user.cell, cell->bel, placed_cells,
-                               visit_cells);
-                    placed_count++;
-                    if (placed_count > count_thresh)
-                        return;
-                }
-            }
-            if (net->driver.cell != nullptr && net->driver.cell->bel == BelId()) {
-                place_cell(design, net->driver.cell, cell->bel, placed_cells,
-                           visit_cells);
-                placed_count++;
-            }
-            if (placed_count > count_thresh)
-                return;
-        }
-    }
-
 }
 
 void place_design_heuristic(Design *design)
@@ -241,21 +192,11 @@ void place_design_heuristic(Design *design)
         }
     }
     log_info("place_constraints placed %d\n", placed_cells);
-    while (placed_cells < total_cells) {
-        if (!visit_cells.empty()) {
-            CellInfo *next = visit_cells.front();
-            visit_cells.pop();
-            place_cell_neighbours(design, next, placed_cells, visit_cells);
-        } else {
-            // Nothing to visit (netlist is split), pick the next unplaced cell
-            for (auto cell : design->cells) {
-                CellInfo *ci = cell.second;
-                if (ci->bel == BelId()) {
-                    place_cell(design, ci, BelId(), placed_cells, visit_cells);
-                    break;
-                }
-            }
-        }
+    for (auto cell : design->cells) {
+        CellInfo *ci = cell.second;
+        if (ci->bel == BelId())
+            place_cell(design, ci);
+        placed_cells++;
         log_info("placed %d/%d\n", placed_cells, total_cells);
     }
 }
-- 
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