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ice40: During global promotion, only promote if this will actually fit !

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We need to take into account the global networks that are already used
and possibly locked to know what we can promote since all networks
can't drive resets / clock-enables

Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
This commit is contained in:
Sylvain Munaut 2018-11-26 11:05:18 +01:00
parent a79f0db749
commit 584e8c58a6
1 changed files with 32 additions and 6 deletions
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38
ice40/pack.cc
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@ -587,10 +587,36 @@ static void promote_globals(Context *ctx)
} }
} }
int prom_globals = 0, prom_resets = 0, prom_cens = 0, prom_logics = 0; int prom_globals = 0, prom_resets = 0, prom_cens = 0, prom_logics = 0;
int gbs_available = 8; int gbs_available = 8, resets_available = 4, cens_available = 4;
for (auto &cell : ctx->cells) for (auto &cell : ctx->cells)
if (is_gbuf(ctx, cell.second.get())) if (is_gbuf(ctx, cell.second.get())) {
/* One less buffer available */
--gbs_available; --gbs_available;
/* And possibly limits what we can promote */
if (cell.second->attrs.find(ctx->id("BEL")) != cell.second->attrs.end()) {
/* If the SB_GB is locked, doesn't matter what it drives */
BelId bel = ctx->getBelByName(ctx->id(cell.second->attrs[ctx->id("BEL")]));
int glb_id = ctx->getDrivenGlobalNetwork(bel);
if ((glb_id % 2) == 0)
resets_available--;
else if ((glb_id % 2) == 1)
cens_available--;
} else {
/* If it's free to move around, then look at what it drives */
NetInfo *ni = cell.second->ports[id_GLOBAL_BUFFER_OUTPUT].net;
for (auto user : ni->users) {
if (is_reset_port(ctx, user)) {
resets_available--;
break;
} else if (is_enable_port(ctx, user)) {
cens_available--;
break;
}
}
}
}
while (prom_globals < gbs_available) { while (prom_globals < gbs_available) {
auto global_clock = std::max_element(clock_count.begin(), clock_count.end(), auto global_clock = std::max_element(clock_count.begin(), clock_count.end(),
[](const std::pair<IdString, int> &a, const std::pair<IdString, int> &b) { [](const std::pair<IdString, int> &a, const std::pair<IdString, int> &b) {
@ -610,8 +636,8 @@ static void promote_globals(Context *ctx)
return a.second < b.second; return a.second < b.second;
}); });
if (global_clock->second == 0 && prom_logics < 4 && global_logic->second > logic_fanout_thresh && if (global_clock->second == 0 && prom_logics < 4 && global_logic->second > logic_fanout_thresh &&
(global_logic->second > global_cen->second || prom_cens >= 4) && (global_logic->second > global_cen->second || prom_cens >= cens_available) &&
(global_logic->second > global_reset->second || prom_resets >= 4)) { (global_logic->second > global_reset->second || prom_resets >= resets_available)) {
NetInfo *logicnet = ctx->nets[global_logic->first].get(); NetInfo *logicnet = ctx->nets[global_logic->first].get();
insert_global(ctx, logicnet, false, false, true); insert_global(ctx, logicnet, false, false, true);
++prom_globals; ++prom_globals;
@ -620,7 +646,7 @@ static void promote_globals(Context *ctx)
reset_count.erase(logicnet->name); reset_count.erase(logicnet->name);
cen_count.erase(logicnet->name); cen_count.erase(logicnet->name);
logic_count.erase(logicnet->name); logic_count.erase(logicnet->name);
} else if (global_reset->second > global_clock->second && prom_resets < 4) { } else if (global_reset->second > global_clock->second && prom_resets < resets_available) {
NetInfo *rstnet = ctx->nets[global_reset->first].get(); NetInfo *rstnet = ctx->nets[global_reset->first].get();
insert_global(ctx, rstnet, true, false, false); insert_global(ctx, rstnet, true, false, false);
++prom_globals; ++prom_globals;
@ -629,7 +655,7 @@ static void promote_globals(Context *ctx)
reset_count.erase(rstnet->name); reset_count.erase(rstnet->name);
cen_count.erase(rstnet->name); cen_count.erase(rstnet->name);
logic_count.erase(rstnet->name); logic_count.erase(rstnet->name);
} else if (global_cen->second > global_clock->second && prom_cens < 4 && } else if (global_cen->second > global_clock->second && prom_cens < cens_available &&
global_cen->second > enable_fanout_thresh) { global_cen->second > enable_fanout_thresh) {
NetInfo *cennet = ctx->nets[global_cen->first].get(); NetInfo *cennet = ctx->nets[global_cen->first].get();
insert_global(ctx, cennet, false, true, false); insert_global(ctx, cennet, false, true, false);