rr_graph_timing_params.h File Reference

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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 12 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 = std::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] = std::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 || to_rr_type == IPIN);
                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 or IPIN */
                    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) {
                            vpr_printf(TIO_MESSAGE_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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