|
| 1 | +/** |
| 2 | + * @file |
| 3 | + * @author Alex Singer |
| 4 | + * @date September 2024 |
| 5 | + * @brief Definition of the gen_ap_netlist_from_atoms method, used for |
| 6 | + * generating an APNetlist from the results of the Prepacker. |
| 7 | + */ |
| 8 | + |
| 9 | +#include "gen_ap_netlist_from_atoms.h" |
| 10 | +#include "ap_netlist.h" |
| 11 | +#include "atom_netlist.h" |
| 12 | +#include "atom_netlist_fwd.h" |
| 13 | +#include "netlist_fwd.h" |
| 14 | +#include "partition.h" |
| 15 | +#include "partition_region.h" |
| 16 | +#include "prepack.h" |
| 17 | +#include "region.h" |
| 18 | +#include "user_place_constraints.h" |
| 19 | +#include "vpr_types.h" |
| 20 | +#include "vtr_assert.h" |
| 21 | +#include "vtr_geometry.h" |
| 22 | +#include "vtr_time.h" |
| 23 | +#include <unordered_set> |
| 24 | +#include <vector> |
| 25 | + |
| 26 | +APNetlist gen_ap_netlist_from_atoms(const AtomNetlist& atom_netlist, |
| 27 | + const Prepacker& prepacker, |
| 28 | + const UserPlaceConstraints& constraints) { |
| 29 | + // Create a scoped timer for reading the atom netlist. |
| 30 | + vtr::ScopedStartFinishTimer timer("Read Atom Netlist to AP Netlist"); |
| 31 | + |
| 32 | + // FIXME: What to do about the name and ID in this context? For now just |
| 33 | + // using empty strings. |
| 34 | + APNetlist ap_netlist; |
| 35 | + |
| 36 | + // Add the APBlocks based on the atom block molecules. This essentially |
| 37 | + // creates supernodes. |
| 38 | + // Each AP block has the name of the first atom block in the molecule. |
| 39 | + // Each port is named "<atom_blk_name>_<atom_port_name>" |
| 40 | + // Each net has the exact same name as in the atom netlist |
| 41 | + for (AtomBlockId atom_blk_id : atom_netlist.blocks()) { |
| 42 | + // Get the molecule of this block |
| 43 | + t_pack_molecule* mol = prepacker.get_atom_molecule(atom_blk_id); |
| 44 | + // Create the AP block (if not already done) |
| 45 | + const std::string& first_blk_name = atom_netlist.block_name(mol->atom_block_ids[0]); |
| 46 | + APBlockId ap_blk_id = ap_netlist.create_block(first_blk_name, mol); |
| 47 | + // Add the ports and pins of this block to the supernode |
| 48 | + for (AtomPortId atom_port_id : atom_netlist.block_ports(atom_blk_id)) { |
| 49 | + BitIndex port_width = atom_netlist.port_width(atom_port_id); |
| 50 | + PortType port_type = atom_netlist.port_type(atom_port_id); |
| 51 | + const std::string& port_name = atom_netlist.port_name(atom_port_id); |
| 52 | + const std::string& block_name = atom_netlist.block_name(atom_blk_id); |
| 53 | + // The port name needs to be made unique for the supernode (two |
| 54 | + // joined blocks may have the same port name) |
| 55 | + std::string ap_port_name = block_name + "_" + port_name; |
| 56 | + APPortId ap_port_id = ap_netlist.create_port(ap_blk_id, ap_port_name, port_width, port_type); |
| 57 | + for (AtomPinId atom_pin_id : atom_netlist.port_pins(atom_port_id)) { |
| 58 | + BitIndex port_bit = atom_netlist.pin_port_bit(atom_pin_id); |
| 59 | + PinType pin_type = atom_netlist.pin_type(atom_pin_id); |
| 60 | + bool pin_is_const = atom_netlist.pin_is_constant(atom_pin_id); |
| 61 | + AtomNetId pin_atom_net_id = atom_netlist.pin_net(atom_pin_id); |
| 62 | + const std::string& pin_atom_net_name = atom_netlist.net_name(pin_atom_net_id); |
| 63 | + APNetId pin_ap_net_id = ap_netlist.create_net(pin_atom_net_name); |
| 64 | + ap_netlist.create_pin(ap_port_id, port_bit, pin_ap_net_id, pin_type, pin_is_const); |
| 65 | + } |
| 66 | + } |
| 67 | + } |
| 68 | + |
| 69 | + // Fix the block locations given by the VPR constraints |
| 70 | + for (APBlockId ap_blk_id : ap_netlist.blocks()) { |
| 71 | + const t_pack_molecule* mol = ap_netlist.block_molecule(ap_blk_id); |
| 72 | + for (AtomBlockId mol_atom_blk_id : mol->atom_block_ids) { |
| 73 | + PartitionId part_id = constraints.get_atom_partition(mol_atom_blk_id); |
| 74 | + if (!part_id.is_valid()) |
| 75 | + continue; |
| 76 | + // We should not fix a block twice. This would imply that a molecule |
| 77 | + // contains two fixed blocks. This would only make sense if the blocks |
| 78 | + // were fixed to the same location. I am not sure if that is even |
| 79 | + // possible. |
| 80 | + VTR_ASSERT(ap_netlist.block_mobility(ap_blk_id) == APBlockMobility::MOVEABLE); |
| 81 | + // Get the partition region. |
| 82 | + const PartitionRegion& partition_pr = constraints.get_partition_pr(part_id); |
| 83 | + // TODO: Either handle the union of legal locations or turn into a |
| 84 | + // proper error. |
| 85 | + VTR_ASSERT(partition_pr.get_regions().size() == 1 && "AP: Each partition should contain only one region for AP right now."); |
| 86 | + const Region& region = partition_pr.get_regions()[0]; |
| 87 | + // Get the x and y. |
| 88 | + const vtr::Rect<int>& region_rect = region.get_rect(); |
| 89 | + VTR_ASSERT(region_rect.xmin() == region_rect.xmax() && "AP: Expect each region to be a single point in x!"); |
| 90 | + VTR_ASSERT(region_rect.ymin() == region_rect.ymax() && "AP: Expect each region to be a single point in y!"); |
| 91 | + int blk_x_loc = region_rect.xmin(); |
| 92 | + int blk_y_loc = region_rect.ymin(); |
| 93 | + // Get the layer. |
| 94 | + VTR_ASSERT(region.get_layer_range().first == region.get_layer_range().second && "AP: Expect each region to be a single point in layer!"); |
| 95 | + int blk_layer_num = region.get_layer_range().first; |
| 96 | + // Get the sub_tile (if fixed). |
| 97 | + int blk_sub_tile = APFixedBlockLoc::UNFIXED_DIM; |
| 98 | + if (region.get_sub_tile() != NO_SUBTILE) |
| 99 | + blk_sub_tile = region.get_sub_tile(); |
| 100 | + // Set the fixed block location. |
| 101 | + APFixedBlockLoc loc = {blk_x_loc, blk_y_loc, blk_layer_num, blk_sub_tile}; |
| 102 | + ap_netlist.set_block_loc(ap_blk_id, loc); |
| 103 | + } |
| 104 | + } |
| 105 | + |
| 106 | + // Cleanup the netlist by removing undesirable nets. |
| 107 | + // Currently undesirable nets are nets that are: |
| 108 | + // - ignored for placement |
| 109 | + // - a global net |
| 110 | + // - connected to 1 or fewer unique blocks |
| 111 | + // - connected to only fixed blocks |
| 112 | + // TODO: Allow the user to pass a threshold so we can remove high-fanout nets. |
| 113 | + auto remove_net = [&](APNetId net_id) { |
| 114 | + // Remove all pins associated with this net |
| 115 | + for (APPinId pin_id : ap_netlist.net_pins(net_id)) |
| 116 | + ap_netlist.remove_pin(pin_id); |
| 117 | + // Remove the net |
| 118 | + ap_netlist.remove_net(net_id); |
| 119 | + }; |
| 120 | + for (APNetId ap_net_id : ap_netlist.nets()) { |
| 121 | + // Is the net ignored for placement, if so remove |
| 122 | + const std::string& net_name = ap_netlist.net_name(ap_net_id); |
| 123 | + AtomNetId atom_net_id = atom_netlist.find_net(net_name); |
| 124 | + VTR_ASSERT(atom_net_id.is_valid()); |
| 125 | + if (atom_netlist.net_is_ignored(atom_net_id)) { |
| 126 | + remove_net(ap_net_id); |
| 127 | + continue; |
| 128 | + } |
| 129 | + // Is the net global, if so remove |
| 130 | + if (atom_netlist.net_is_global(atom_net_id)) { |
| 131 | + remove_net(ap_net_id); |
| 132 | + continue; |
| 133 | + } |
| 134 | + // Get the unique blocks connectioned to this net |
| 135 | + std::unordered_set<APBlockId> net_blocks; |
| 136 | + for (APPinId ap_pin_id : ap_netlist.net_pins(ap_net_id)) { |
| 137 | + net_blocks.insert(ap_netlist.pin_block(ap_pin_id)); |
| 138 | + } |
| 139 | + // If connected to 1 or fewer unique blocks, remove |
| 140 | + if (net_blocks.size() <= 1) { |
| 141 | + remove_net(ap_net_id); |
| 142 | + continue; |
| 143 | + } |
| 144 | + // If all the connected blocks are fixed, remove |
| 145 | + bool is_all_fixed = true; |
| 146 | + for (APBlockId ap_blk_id : net_blocks) { |
| 147 | + if (ap_netlist.block_mobility(ap_blk_id) == APBlockMobility::MOVEABLE) { |
| 148 | + is_all_fixed = false; |
| 149 | + break; |
| 150 | + } |
| 151 | + } |
| 152 | + if (is_all_fixed) { |
| 153 | + remove_net(ap_net_id); |
| 154 | + continue; |
| 155 | + } |
| 156 | + } |
| 157 | + ap_netlist.remove_and_compress(); |
| 158 | + |
| 159 | + // TODO: Should we cleanup the blocks? For example if there is no path |
| 160 | + // from a fixed block to a given moveable block, then that moveable |
| 161 | + // block can be removed (since it can literally go anywhere). |
| 162 | + // - This would be useful to detect and use throughout; but may cause some |
| 163 | + // issues if we just remove them. When and where will they eventually |
| 164 | + // be placed? |
| 165 | + // - Perhaps we can add a flag in the netlist to each of these blocks and |
| 166 | + // during the solving stage we can ignore them. |
| 167 | + // For now, leave this alone; but should check if the matrix becomes |
| 168 | + // ill-formed and causes problems. |
| 169 | + |
| 170 | + // Verify that the netlist was created correctly. |
| 171 | + VTR_ASSERT(ap_netlist.verify()); |
| 172 | + |
| 173 | + return ap_netlist; |
| 174 | +} |
| 175 | + |
0 commit comments