SRC/rr_graph_timing_params.c File Reference

#include <assert.h>
#include "util.h"
#include "vpr_types.h"
#include "globals.h"
#include "rr_graph.h"
#include "rr_graph_util.h"
#include "rr_graph2.h"
#include "rr_graph_timing_params.h"

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Functions
void	add_rr_graph_C_from_switches (float C_ipin_cblock)

---

Function Documentation

void add_rr_graph_C_from_switches

(

float

C_ipin_cblock

)

Definition at line 16 of file rr_graph_timing_params.c.

{

/* This routine finishes loading the C elements of the rr_graph. It assumes *
 * that when you call it the CHANX and CHANY nodes have had their C set to  *
 * their metal capacitance, and everything else has C set to 0.  The graph  *
 * connectivity (edges, switch types etc.) must all be loaded too.  This    *
 * routine will add in the capacitance on the CHANX and CHANY nodes due to: *
 *                                                                          *
 * 1) The output capacitance of the switches coming from OPINs;             *
 * 2) The input and output capacitance of the switches between the various  *
 *    wiring (CHANX and CHANY) segments; and                                *
 * 3) The input capacitance of the buffers separating routing tracks from   *
 *    the connection block inputs.                                          */


    int inode, iedge, switch_index, to_node, maxlen;
    int icblock, isblock, iseg_low, iseg_high;
    float Cin, Cout;
    t_rr_type from_rr_type, to_rr_type;
    boolean *cblock_counted;    /* [0..max(nx,ny)] -- 0th element unused. */
    float *buffer_Cin;          /* [0..max(nx,ny)] */
    boolean buffered;
    float *Couts_to_add;        /* UDSD */

    maxlen = max(nx, ny) + 1;
    cblock_counted = (boolean *) my_calloc(maxlen, sizeof(boolean));
    buffer_Cin = (float *)my_calloc(maxlen, sizeof(float));

    for(inode = 0; inode < num_rr_nodes; inode++)
        {

            from_rr_type = rr_node[inode].type;

            if(from_rr_type == CHANX || from_rr_type == CHANY)
                {

                    for(iedge = 0; iedge < rr_node[inode].num_edges; iedge++)
                        {

                            to_node = rr_node[inode].edges[iedge];
                            to_rr_type = rr_node[to_node].type;

                            if(to_rr_type == CHANX || to_rr_type == CHANY)
                                {

                                    switch_index =
                                        rr_node[inode].switches[iedge];
                                    Cin = switch_inf[switch_index].Cin;
                                    Cout = switch_inf[switch_index].Cout;
                                    buffered =
                                        switch_inf[switch_index].buffered;

                                    /* If both the switch from inode to to_node and the switch from *
                                     * to_node back to inode use bidirectional switches (i.e. pass  *
                                     * transistors), there will only be one physical switch for     *
                                     * both edges.  Hence, I only want to count the capacitance of  *
                                     * that switch for one of the two edges.  (Note:  if there is   *
                                     * a pass transistor edge from x to y, I always build the graph *
                                     * so that there is a corresponding edge using the same switch  *
                                     * type from y to x.) So, I arbitrarily choose to add in the    *
                                     * capacitance in that case of a pass transistor only when      *
                                     * processing the the lower inode number.                       *
                                     * If an edge uses a buffer I always have to add in the output  *
                                     * capacitance.  I assume that buffers are shared at the same   *
                                     * (i,j) location, so only one input capacitance needs to be    *
                                     * added for all the buffered switches at that location.  If    *
                                     * the buffers at that location have different sizes, I use the *
                                     * input capacitance of the largest one.                        */

                                    if(!buffered && inode < to_node)
                                        {       /* Pass transistor. */
                                            rr_node[inode].C += Cin;
                                            rr_node[to_node].C += Cout;
                                        }

                                    else if(buffered)
                                        {
                                            /* Prevent double counting of capacitance for UDSD */
                                            if(rr_node[to_node].drivers !=
                                               SINGLE)
                                                {
                                                    /* For multiple-driver architectures the output capacitance can
                                                     * be added now since each edge is actually a driver */
                                                    rr_node[to_node].C +=
                                                        Cout;
                                                }
                                            isblock =
                                                seg_index_of_sblock(inode,
                                                                    to_node);
                                            buffer_Cin[isblock] =
                                                max(buffer_Cin[isblock], Cin);
                                        }

                                }
                            /* End edge to CHANX or CHANY node. */
                            else if(to_rr_type == IPIN)
                                {

                                    /* Code below implements sharing of the track to connection     *
                                     * box buffer.  I assume there is one such buffer at every      *
                                     * segment of the wire at which at least one logic block input  *
                                     * connects.                                                    */

                                    icblock =
                                        seg_index_of_cblock(from_rr_type,
                                                            to_node);
                                    if(cblock_counted[icblock] == FALSE)
                                        {
                                            rr_node[inode].C += C_ipin_cblock;
                                            cblock_counted[icblock] = TRUE;
                                        }
                                }
                        }       /* End loop over all edges of a node. */

                    /* Reset the cblock_counted and buffer_Cin arrays, and add buf Cin. */

                    /* Method below would be faster for very unpopulated segments, but I  *
                     * think it would be slower overall for most FPGAs, so commented out. */

                    /*   for (iedge=0;iedge<rr_node[inode].num_edges;iedge++) {
                     * to_node = rr_node[inode].edges[iedge];
                     * if (rr_node[to_node].type == IPIN) {
                     * icblock = seg_index_of_cblock (from_rr_type, to_node);
                     * cblock_counted[icblock] = FALSE;
                     * }
                     * }     */

                    if(from_rr_type == CHANX)
                        {
                            iseg_low = rr_node[inode].xlow;
                            iseg_high = rr_node[inode].xhigh;
                        }
                    else
                        {       /* CHANY */
                            iseg_low = rr_node[inode].ylow;
                            iseg_high = rr_node[inode].yhigh;
                        }

                    for(icblock = iseg_low; icblock <= iseg_high; icblock++)
                        {
                            cblock_counted[icblock] = FALSE;
                        }

                    for(isblock = iseg_low - 1; isblock <= iseg_high;
                        isblock++)
                        {
                            rr_node[inode].C += buffer_Cin[isblock];    /* Biggest buf Cin at loc */
                            buffer_Cin[isblock] = 0.;
                        }

                }
            /* End node is CHANX or CHANY */
            else if(from_rr_type == OPIN)
                {

                    for(iedge = 0; iedge < rr_node[inode].num_edges; iedge++)
                        {
                            switch_index = rr_node[inode].switches[iedge];
                            /* UDSD by ICK Start */
                            to_node = rr_node[inode].edges[iedge];
                            to_rr_type = rr_node[to_node].type;
                            assert(to_rr_type == CHANX
                                   || to_rr_type == CHANY);
                            if(rr_node[to_node].drivers != SINGLE)
                                {
                                    Cout = switch_inf[switch_index].Cout;
                                    to_node = rr_node[inode].edges[iedge];      /* Will be CHANX or CHANY */
                                    rr_node[to_node].C += Cout;
                                }
                        }
                }
            /* End node is OPIN. */
        }                       /* End for all nodes. */

    /* Now we need to add any cout loads for nets that we previously didn't process
     * Current structures only keep switch information from a node to the next node and
     * not the reverse.  Therefore I need to go through all the possible edges to figure 
     * out what the Cout's should be */
    Couts_to_add = (float *)my_calloc(num_rr_nodes, sizeof(float));
    for(inode = 0; inode < num_rr_nodes; inode++)
        {
            for(iedge = 0; iedge < rr_node[inode].num_edges; iedge++)
                {
                    switch_index = rr_node[inode].switches[iedge];
                    to_node = rr_node[inode].edges[iedge];
                    to_rr_type = rr_node[to_node].type;
                    if(to_rr_type == CHANX || to_rr_type == CHANY)
                        {
                            if(rr_node[to_node].drivers == SINGLE)
                                {
                                    /* Cout was not added in these cases */
                                    if(Couts_to_add[to_node] != 0)
                                        {
                                            /* We've already found a Cout to add to this node
                                             * We could take the max of all possibilities but
                                             * instead I will fail if there are conflicting Couts */
                                            if(Couts_to_add[to_node] !=
                                               switch_inf[switch_index].Cout)
                                                {
                                                    printf
                                                        ("Error: A single driver resource (%i) is driven by different Cout's (%e!=%e)\n",
                                                         to_node,
                                                         Couts_to_add
                                                         [to_node],
                                                         switch_inf
                                                         [switch_index].Cout);
                                                    exit(1);
                                                }
                                        }
                                    Couts_to_add[to_node] =
                                        switch_inf[switch_index].Cout;

                                }
                        }
                }
        }
    for(inode = 0; inode < num_rr_nodes; inode++)
        {
            rr_node[inode].C += Couts_to_add[inode];
        }
    free(Couts_to_add);
    free(cblock_counted);
    free(buffer_Cin);
}

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