Merge branch 'fix_budget_overrides' into assign_budget_speedup

Conflicts:
	common/timing.cc

3 files changed, 25 insertions, 28 deletions

diff --git a/common/timing.cc b/common/timing.cc
index 69fdd29f..72093183 100644
--- a/common/timing.cc
+++ b/common/timing.cc
@@ -57,22 +57,26 @@ struct Timing
 
     delay_t follow_net(NetInfo *net, int path_length, delay_t slack)
     {
-        delay_t net_budget = slack / (path_length + 1);
+        const delay_t default_budget = slack / (path_length + 1);
+        delay_t net_budget = default_budget;
         for (auto &usr : net->users) {
+            auto delay = net_delays ? ctx->getNetinfoRouteDelay(net, usr) : delay_t();
             if (crit_path)
                 current_path.push_back(&usr);
-            // If budget override is less than existing budget, then do not increment
-            // path length
-            int pl = path_length + 1;
-            auto budget = net_budget;
-            if (ctx->getBudgetOverride(net, usr, budget) && budget < net_budget) {
-                net_budget = budget;
-                pl = std::max(1, path_length);
+            // If budget override exists, use that value and do not increment path_length
+            auto budget = default_budget;
+            if (ctx->getBudgetOverride(net, usr, budget)) {
+                if (update)
+                    usr.budget = std::min(usr.budget, budget);
+                budget = follow_user_port(usr, path_length, slack - budget);
+                net_budget = std::min(net_budget, budget);
+            }
+            else {
+                budget = follow_user_port(usr, path_length + 1, slack - delay);
+                net_budget = std::min(net_budget, budget);
+                if (update)
+                    usr.budget = std::min(usr.budget, delay + budget);
             }
-            auto delay = net_delays ? ctx->getNetinfoRouteDelay(net, usr) : delay_t();
-            net_budget = std::min(net_budget, follow_user_port(usr, pl, slack - delay));
-            if (update)
-                usr.budget = std::min(usr.budget, delay + net_budget);
             if (crit_path)
                 current_path.pop_back();
         }
@@ -222,8 +226,7 @@ struct Timing
                 if (ctx->getPortClock(usr.cell, usr.port) != IdString()) {
                 } else {
                     auto net_delay = ctx->getNetinfoRouteDelay(net, usr);
-                    delay_t budget;
-                    auto budget_override = ctx->getBudgetOverride(net, usr, budget);
+                    auto budget_override = ctx->getBudgetOverride(net, usr, net_delay);
                     auto usr_arrival = net_arrival + net_delay;
                     // Follow outputs of the user
                     for (auto port : usr.cell->ports) {
@@ -252,15 +255,12 @@ struct Timing
             auto& net_min_remaining_budget = nd.min_remaining_budget;
             for (auto &usr : net->users) {
                 const auto net_delay = ctx->getNetinfoRouteDelay(net, usr);
-                auto budget_override = ctx->getBudgetOverride(net, usr, usr.budget);
+                auto budget_override = ctx->getBudgetOverride(net, usr, net_delay);
                 if (ctx->getPortClock(usr.cell, usr.port) != IdString()) {
                     const auto net_arrival = nd.max_arrival;
                     auto path_budget = clk_period - (net_arrival + net_delay);
-                    auto budget_share = path_budget / net_length_plus_one;
-                    if (budget_override)
-                        budget_share = 0;
-                    else
-                        usr.budget = std::min(usr.budget, net_delay + budget_share);
+                    auto budget_share = budget_override ? 0 : path_budget / net_length_plus_one;
+                    usr.budget = std::min(usr.budget, net_delay + budget_share);
                     net_min_remaining_budget = std::min(net_min_remaining_budget, path_budget - budget_share);
 
                     min_slack = std::min(min_slack, path_budget);
@@ -277,11 +277,8 @@ struct Timing
                             bool is_path = ctx->getCellDelay(usr.cell, usr.port, port.first, comb_delay);
                             if (is_path) {
                                 auto path_budget = net_data.at(port.second.net).min_remaining_budget;
-                                auto budget_share = path_budget / net_length_plus_one;
-                                if (budget_override)
-                                    budget_share = 0;
-                                else
-                                    usr.budget = std::min(usr.budget, net_delay + budget_share);
+                                auto budget_share = budget_override ? 0 : path_budget / net_length_plus_one;
+                                usr.budget = std::min(usr.budget, net_delay + budget_share);
                                 net_min_remaining_budget = std::min(net_min_remaining_budget, path_budget - budget_share);
                             }
                         }
diff --git a/docs/archapi.md b/docs/archapi.md
index 79562fe6..222b9f78 100644
--- a/docs/archapi.md
+++ b/docs/archapi.md
@@ -402,9 +402,9 @@ Convert an `delay_t` to an actual real-world delay in nanoseconds.
 
 Convert a `delay_t` to an integer for checksum calculations.
 
-### delay\_t getBudgetOverride(const NetInfo \*net\_info, const PortRef &sink, delay\_t budget) const
+### bool getBudgetOverride(const NetInfo \*net\_info, const PortRef &sink, delay\_t &budget) const
 
-Overwrite or modify the timing budget for a given arc. Returns the new budget.
+Overwrite or modify (in-place) the timing budget for a given arc. Returns a bool to indicate whether this was done.
 
 Flow Methods
 ------------
diff --git a/ice40/arch.cc b/ice40/arch.cc
index b8bb13ea..1e7a383b 100644
--- a/ice40/arch.cc
+++ b/ice40/arch.cc
@@ -640,7 +640,7 @@ std::vector<GroupId> Arch::getGroupGroups(GroupId group) const
 bool Arch::getBudgetOverride(const NetInfo *net_info, const PortRef &sink, delay_t &budget) const
 {
     const auto &driver = net_info->driver;
-    if (driver.port == id_cout) {
+    if (driver.port == id_cout && sink.port == id_cin) {
         auto driver_loc = getBelLocation(driver.cell->bel);
         auto sink_loc = getBelLocation(sink.cell->bel);
         if (driver_loc.y == sink_loc.y)