[AP] Partial Legalizer

This adds the Patial Legalizer block into VPR. A Partial Legalizer takes
a partial placement (which likely has many overlapping blocks and is
very illegal with blocks in the wrong tiles) and creates a more legal
partial placement. These are often called spreaders since their main
task is to spread blocks away from each other (the solver tends to put
blocks on top of each other).

Added a multi-commodity flow-based spreading partial legalizer based on
the work by Darav et al. This algorithm was modified to work within the
VPR infrastructure on any hypothetical architecture which can be
expressed in VPR.

Author: AlexandreSinger

vpr/src/analytical_place/analytical_placement_flow.cpp

@@ -13,6 +13,7 @@
 #include "full_legalizer.h"
 #include "gen_ap_netlist_from_atoms.h"
 #include "globals.h"
+#include "partial_legalizer.h"
 #include "partial_placement.h"
 #include "prepack.h"
 #include "user_place_constraints.h"
@@ -53,6 +54,7 @@ static void print_ap_netlist_stats(const APNetlist& netlist) {
     VTR_LOG("\t\tAverage Fanout: %.2f\n", average_fanout);
     VTR_LOG("\t\tHighest Fanout: %zu\n", highest_fanout);
     VTR_LOG("\tPins: %zu\n", netlist.pins().size());
+    VTR_LOG("\n");
 }
 
 void run_analytical_placement_flow(t_vpr_setup& vpr_setup) {
@@ -77,11 +79,16 @@ void run_analytical_placement_flow(t_vpr_setup& vpr_setup) {
     print_ap_netlist_stats(ap_netlist);
 
     // Run the Global Placer
-    //  For now, just runs the solver.
+    //  For now, just runs the solver and partial legalizer 10 times arbitrarily.
     PartialPlacement p_placement(ap_netlist);
     std::unique_ptr<AnalyticalSolver> solver = make_analytical_solver(e_analytical_solver::QP_HYBRID,
                                                                       ap_netlist);
-    solver->solve(0, p_placement);
+    std::unique_ptr<PartialLegalizer> legalizer = make_partial_legalizer(e_partial_legalizer::FLOW_BASED,
+                                                                         ap_netlist);
+    for (size_t i = 0; i < 10; i++) {
+        solver->solve(i, p_placement);
+        legalizer->legalize(p_placement);
+    }
 
     // Verify that the partial placement is valid before running the full
     // legalizer.

vpr/src/analytical_place/full_legalizer.cpp

@@ -2,7 +2,9 @@
  * @file
  * @author  Alex Singer
  * @date    September 2024
- * @brief   Implements the full legalizer in the AP flow.
+ * @brief   Implements the full legalizer in the AP flow. The Full Legalizer
+ *          takes a partial placement and fully legalizes it. This involves
+ *          creating legal clusters and placing them into valid tile sites.
  */
 
 #include "full_legalizer.h"
@@ -29,6 +31,7 @@
 #include "vpr_error.h"
 #include "vpr_types.h"
 #include "vtr_assert.h"
+#include "vtr_geometry.h"
 #include "vtr_ndmatrix.h"
 #include "vtr_strong_id.h"
 #include "vtr_time.h"
@@ -122,9 +125,8 @@ class APClusterPlacer {
                        const t_physical_tile_loc& tile_loc,
                        int sub_tile) {
         const DeviceContext& device_ctx = g_vpr_ctx.device();
-        // FIXME: THIS MUST TAKE INTO ACCOUNT THE CONSTRAINTS AS WELL!!!
-        //  - Right now it is just implied.
-        //  - Will work but is unstable.
+        const FloorplanningContext& floorplanning_ctx = g_vpr_ctx.floorplanning();
+        const ClusteringContext& cluster_ctx = g_vpr_ctx.clustering();
         const auto& block_locs = g_vpr_ctx.placement().block_locs();
         auto& blk_loc_registry = g_vpr_ctx.mutable_placement().mutable_blk_loc_registry();
         VTR_ASSERT(!is_block_placed(clb_blk_id, block_locs) && "Block already placed. Is this intentional?");
@@ -137,11 +139,24 @@ class APClusterPlacer {
         if (device_ctx.grid.get_physical_type(tile_loc)->sub_tiles.size() == 0)
             return false;
         VTR_ASSERT(sub_tile >= 0 && sub_tile < device_ctx.grid.get_physical_type(tile_loc)->capacity);
-        // FIXME: Do this better.
-        //  - May need to try all the sub-tiles in a location.
-        //  - https://github.com/AlexandreSinger/vtr-verilog-to-routing/blob/feature-analytical-placer/vpr/src/place/initial_placement.cpp#L755
-        to_loc.sub_tile = sub_tile;
-        return try_place_macro(pl_macro, to_loc, blk_loc_registry);
+        // Check if this cluster is constrained and this location is legal.
+        if (is_cluster_constrained(clb_blk_id)) {
+            const auto& cluster_constraints = floorplanning_ctx.cluster_constraints;
+            if (cluster_constraints[clb_blk_id].is_loc_in_part_reg(to_loc))
+                return false;
+        }
+        // If the location is legal, try to exhaustively place it at this tile
+        // location. This should try all sub_tiles.
+        PartitionRegion pr;
+        vtr::Rect<int> rect(tile_loc.x, tile_loc.y, tile_loc.x, tile_loc.y);
+        pr.add_to_part_region(Region(rect, to_loc.layer));
+        const ClusteredNetlist& clb_nlist = cluster_ctx.clb_nlist;
+        t_logical_block_type_ptr block_type = clb_nlist.block_type(clb_blk_id);
+        enum e_pad_loc_type pad_loc_type = g_vpr_ctx.device().pad_loc_type;
+        // FIXME: This currently ignores the sub_tile. Was running into issues
+        //        with trying to force clusters to specific sub_tiles.
+        return try_place_macro_exhaustively(pl_macro, pr, block_type,
+                                            pad_loc_type, blk_loc_registry);
     }
 
     // This is not the best way of doing things, but its the simplest. Given a
@@ -352,10 +367,6 @@ void FullLegalizer::place_clusters(const ClusteredNetlist& clb_nlist,
         bool placed = ap_cluster_placer.place_cluster(cluster_blk_id, tile_loc, blk_sub_tile);
         if (placed)
             continue;
-        // FIXME: Should now try all sub-tiles at this tile location.
-        //  - May need to try all the sub-tiles in a location.
-        //  - however this may need to be done after.
-        //  - https://github.com/AlexandreSinger/vtr-verilog-to-routing/blob/feature-analytical-placer/vpr/src/place/initial_placement.cpp#L755
 
         // Add to list of unplaced clusters.
         unplaced_clusters.push_back(cluster_blk_id);