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ecp5: Optimise DCC placement

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Signed-off-by: David Shah <davey1576@gmail.com>
This commit is contained in:
David Shah 2018-10-14 13:22:47 +01:00
parent bda94aa5a5
commit 1fc2318c53
1 changed files with 12 additions and 3 deletions
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15
ecp5/globals.cc
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@ -24,7 +24,7 @@
#include "cells.h" #include "cells.h"
#include "log.h" #include "log.h"
#include "nextpnr.h" #include "nextpnr.h"
#include "place_common.h"
#define fmt_str(x) (static_cast<const std::ostringstream &>(std::ostringstream() << x).str()) #define fmt_str(x) (static_cast<const std::ostringstream &>(std::ostringstream() << x).str())
NEXTPNR_NAMESPACE_BEGIN NEXTPNR_NAMESPACE_BEGIN
@ -260,15 +260,24 @@ class Ecp5GlobalRouter
// Attempt to place a DCC // Attempt to place a DCC
void place_dcc(CellInfo *dcc) void place_dcc(CellInfo *dcc)
{ {
BelId best_bel;
wirelen_t best_wirelen = 9999999;
for (auto bel : ctx->getBels()) { for (auto bel : ctx->getBels()) {
if (ctx->getBelType(bel) == id_DCCA && ctx->checkBelAvail(bel)) { if (ctx->getBelType(bel) == id_DCCA && ctx->checkBelAvail(bel)) {
if (ctx->isValidBelForCell(dcc, bel)) { if (ctx->isValidBelForCell(dcc, bel)) {
ctx->bindBel(bel, dcc, STRENGTH_LOCKED); ctx->bindBel(bel, dcc, STRENGTH_LOCKED);
return; float tns;
wirelen_t wirelen = get_net_metric(ctx, dcc->ports.at(id_CLKI).net, MetricType::WIRELENGTH, tns);
if (wirelen < best_wirelen) {
best_bel = bel;
best_wirelen = wirelen;
}
ctx->unbindBel(bel);
} }
} }
} }
NPNR_ASSERT_FALSE("failed to place dcca"); NPNR_ASSERT(best_bel != BelId());
ctx->bindBel(best_bel, dcc, STRENGTH_LOCKED);
} }
// Insert a DCC into a net to promote it to a global // Insert a DCC into a net to promote it to a global