OpenFPGA/vpr7_x2p/vpr/SRC/route/route_breadth_first.c

306 lines
11 KiB
C
Executable File

#include <stdio.h>
#include "util.h"
#include "vpr_types.h"
#include "globals.h"
#include "route_export.h"
#include "route_common.h"
#include "route_breadth_first.h"
/********************* Subroutines local to this module *********************/
static boolean breadth_first_route_net(int inet, float bend_cost);
static void breadth_first_expand_trace_segment(struct s_trace *start_ptr,
int remaining_connections_to_sink);
static void breadth_first_expand_neighbours(int inode, float pcost, int inet,
float bend_cost);
static void breadth_first_add_source_to_heap(int inet);
/************************ Subroutine definitions ****************************/
boolean try_breadth_first_route(struct s_router_opts router_opts,
t_ivec ** clb_opins_used_locally, int width_fac) {
/* Iterated maze router ala Pathfinder Negotiated Congestion algorithm, *
* (FPGA 95 p. 111). Returns TRUE if it can route this FPGA, FALSE if *
* it can't. */
float pres_fac;
boolean success, is_routable, rip_up_local_opins;
int itry, inet;
/* Usually the first iteration uses a very small (or 0) pres_fac to find *
* the shortest path and get a congestion map. For fast compiles, I set *
* pres_fac high even for the first iteration. */
pres_fac = router_opts.first_iter_pres_fac;
for (itry = 1; itry <= router_opts.max_router_iterations; itry++) {
for (inet = 0; inet < num_nets; inet++) {
if (clb_net[inet].is_global == FALSE) { /* Skip global nets. */
pathfinder_update_one_cost(trace_head[inet], -1, pres_fac);
is_routable = breadth_first_route_net(inet,
router_opts.bend_cost);
/* Impossible to route? (disconnected rr_graph) */
if (!is_routable) {
vpr_printf(TIO_MESSAGE_INFO, "Routing failed.\n");
return (FALSE);
}
pathfinder_update_one_cost(trace_head[inet], 1, pres_fac);
}
}
/* Make sure any CLB OPINs used up by subblocks being hooked directly *
* to them are reserved for that purpose. */
if (itry == 1)
rip_up_local_opins = FALSE;
else
rip_up_local_opins = TRUE;
reserve_locally_used_opins(pres_fac, rip_up_local_opins,
clb_opins_used_locally);
success = feasible_routing();
if (success) {
vpr_printf(TIO_MESSAGE_INFO, "Successfully routed after %d routing iterations.\n", itry);
return (TRUE);
}
if (itry == 1)
pres_fac = router_opts.initial_pres_fac;
else
pres_fac *= router_opts.pres_fac_mult;
pres_fac = std::min(pres_fac, static_cast<float>(HUGE_POSITIVE_FLOAT / 1e5));
pathfinder_update_cost(pres_fac, router_opts.acc_fac);
}
vpr_printf(TIO_MESSAGE_INFO, "Routing failed.\n");
return (FALSE);
}
static boolean breadth_first_route_net(int inet, float bend_cost) {
/* Uses a maze routing (Dijkstra's) algorithm to route a net. The net *
* begins at the net output, and expands outward until it hits a target *
* pin. The algorithm is then restarted with the entire first wire segment *
* included as part of the source this time. For an n-pin net, the maze *
* router is invoked n-1 times to complete all the connections. Inet is *
* the index of the net to be routed. Bends are penalized by bend_cost *
* (which is typically zero for detailed routing and nonzero only for global *
* routing), since global routes with lots of bends are tougher to detailed *
* route (using a detailed router like SEGA). *
* If this routine finds that a net *cannot* be connected (due to a complete *
* lack of potential paths, rather than congestion), it returns FALSE, as *
* routing is impossible on this architecture. Otherwise it returns TRUE. */
int i, inode, prev_node, remaining_connections_to_sink;
float pcost, new_pcost;
struct s_heap *current;
struct s_trace *tptr;
free_traceback(inet);
breadth_first_add_source_to_heap(inet);
mark_ends(inet);
tptr = NULL;
remaining_connections_to_sink = 0;
for (i = 1; i <= clb_net[inet].num_sinks; i++) { /* Need n-1 wires to connect n pins */
breadth_first_expand_trace_segment(tptr, remaining_connections_to_sink);
current = get_heap_head();
if (current == NULL) { /* Infeasible routing. No possible path for net. */
vpr_printf (TIO_MESSAGE_INFO, "Cannot route net #%d (%s) to sink #%d -- no possible path.\n",
inet, clb_net[inet].name, i);
reset_path_costs(); /* Clean up before leaving. */
return (FALSE);
}
inode = current->index;
while (rr_node_route_inf[inode].target_flag == 0) {
pcost = rr_node_route_inf[inode].path_cost;
new_pcost = current->cost;
if (pcost > new_pcost) { /* New path is lowest cost. */
rr_node_route_inf[inode].path_cost = new_pcost;
prev_node = current->u.prev_node;
rr_node_route_inf[inode].prev_node = prev_node;
rr_node_route_inf[inode].prev_edge = current->prev_edge;
if (pcost > 0.99 * HUGE_POSITIVE_FLOAT) /* First time touched. */
add_to_mod_list(&rr_node_route_inf[inode].path_cost);
breadth_first_expand_neighbours(inode, new_pcost, inet,
bend_cost);
}
free_heap_data(current);
current = get_heap_head();
if (current == NULL) { /* Impossible routing. No path for net. */
vpr_printf (TIO_MESSAGE_INFO, "Cannot route net #%d (%s) to sink #%d -- no possible path.\n",
inet, clb_net[inet].name, i);
reset_path_costs();
return (FALSE);
}
inode = current->index;
}
rr_node_route_inf[inode].target_flag--; /* Connected to this SINK. */
remaining_connections_to_sink = rr_node_route_inf[inode].target_flag;
tptr = update_traceback(current, inet);
free_heap_data(current);
}
empty_heap();
reset_path_costs();
return (TRUE);
}
static void breadth_first_expand_trace_segment(struct s_trace *start_ptr,
int remaining_connections_to_sink) {
/* Adds all the rr_nodes in the traceback segment starting at tptr (and *
* continuing to the end of the traceback) to the heap with a cost of zero. *
* This allows expansion to begin from the existing wiring. The *
* remaining_connections_to_sink value is 0 if the route segment ending *
* at this location is the last one to connect to the SINK ending the route *
* segment. This is the usual case. If it is not the last connection this *
* net must make to this SINK, I have a hack to ensure the next connection *
* to this SINK goes through a different IPIN. Without this hack, the *
* router would always put all the connections from this net to this SINK *
* through the same IPIN. With LUTs or cluster-based logic blocks, you *
* should never have a net connecting to two logically-equivalent pins on *
* the same logic block, so the hack will never execute. If your logic *
* block is an and-gate, however, nets might connect to two and-inputs on *
* the same logic block, and since the and-inputs are logically-equivalent, *
* this means two connections to the same SINK. */
struct s_trace *tptr, *next_ptr;
int inode, sink_node, last_ipin_node;
tptr = start_ptr;
if(tptr != NULL && rr_node[tptr->index].type == SINK) {
/* During logical equivalence case, only use one opin */
tptr = tptr->next;
}
if (remaining_connections_to_sink == 0) { /* Usual case. */
while (tptr != NULL) {
node_to_heap(tptr->index, 0., NO_PREVIOUS, NO_PREVIOUS, OPEN, OPEN);
tptr = tptr->next;
}
}
else { /* This case never executes for most logic blocks. */
/* Weird case. Lots of hacks. The cleanest way to do this would be to empty *
* the heap, update the congestion due to the partially-completed route, put *
* the whole route so far (excluding IPINs and SINKs) on the heap with cost *
* 0., and expand till you hit the next SINK. That would be slow, so I *
* do some hacks to enable incremental wavefront expansion instead. */
if (tptr == NULL)
return; /* No route yet */
next_ptr = tptr->next;
last_ipin_node = OPEN; /* Stops compiler from complaining. */
/* Can't put last SINK on heap with NO_PREVIOUS, etc, since that won't let *
* us reach it again. Instead, leave the last traceback element (SINK) off *
* the heap. */
while (next_ptr != NULL) {
inode = tptr->index;
node_to_heap(inode, 0., NO_PREVIOUS, NO_PREVIOUS, OPEN, OPEN);
if (rr_node[inode].type == IPIN)
last_ipin_node = inode;
tptr = next_ptr;
next_ptr = tptr->next;
}
/* This will stop the IPIN node used to get to this SINK from being *
* reexpanded for the remainder of this net's routing. This will make us *
* hook up more IPINs to this SINK (which is what we want). If IPIN *
* doglegs are allowed in the graph, we won't be able to use this IPIN to *
* do a dogleg, since it won't be re-expanded. Shouldn't be a big problem. */
rr_node_route_inf[last_ipin_node].path_cost = -HUGE_POSITIVE_FLOAT;
/* Also need to mark the SINK as having high cost, so another connection can *
* be made to it. */
sink_node = tptr->index;
rr_node_route_inf[sink_node].path_cost = HUGE_POSITIVE_FLOAT;
/* Finally, I need to remove any pending connections to this SINK via the *
* IPIN I just used (since they would result in congestion). Scan through *
* the heap to do this. */
invalidate_heap_entries(sink_node, last_ipin_node);
}
}
static void breadth_first_expand_neighbours(int inode, float pcost, int inet,
float bend_cost) {
/* Puts all the rr_nodes adjacent to inode on the heap. rr_nodes outside *
* the expanded bounding box specified in route_bb are not added to the *
* heap. pcost is the path_cost to get to inode. */
int iconn, to_node, num_edges;
t_rr_type from_type, to_type;
float tot_cost;
num_edges = rr_node[inode].num_edges;
for (iconn = 0; iconn < num_edges; iconn++) {
to_node = rr_node[inode].edges[iconn];
if (rr_node[to_node].xhigh < route_bb[inet].xmin
|| rr_node[to_node].xlow > route_bb[inet].xmax
|| rr_node[to_node].yhigh < route_bb[inet].ymin
|| rr_node[to_node].ylow > route_bb[inet].ymax)
continue; /* Node is outside (expanded) bounding box. */
tot_cost = pcost + get_rr_cong_cost(to_node);
if (bend_cost != 0.) {
from_type = rr_node[inode].type;
to_type = rr_node[to_node].type;
if ((from_type == CHANX && to_type == CHANY)
|| (from_type == CHANY && to_type == CHANX))
tot_cost += bend_cost;
}
node_to_heap(to_node, tot_cost, inode, iconn, OPEN, OPEN);
}
}
static void breadth_first_add_source_to_heap(int inet) {
/* Adds the SOURCE of this net to the heap. Used to start a net's routing. */
int inode;
float cost;
inode = net_rr_terminals[inet][0]; /* SOURCE */
cost = get_rr_cong_cost(inode);
node_to_heap(inode, cost, NO_PREVIOUS, NO_PREVIOUS, OPEN, OPEN);
}