Merge pull request #40 from eddiehung/fix_budget_overrides

Fix budget overrides

8 files changed, 46 insertions, 24 deletions

diff --git a/common/timing.cc b/common/timing.cc
index ae5783cd..d6c46632 100644
--- a/common/timing.cc
+++ b/common/timing.cc
@@ -2,6 +2,7 @@
  *  nextpnr -- Next Generation Place and Route
  *
  *  Copyright (C) 2018  David Shah <david@symbioticeda.com>
+ *  Copyright (C) 2018  Eddie Hung <eddieh@ece.ubc.ca>
  *
  *  Permission to use, copy, modify, and/or distribute this software for any
  *  purpose with or without fee is hereby granted, provided that the above
@@ -48,22 +49,26 @@ 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 = ctx->getBudgetOverride(net, usr, net_budget);
-            if (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();
         }
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/ecp5/arch.cc b/ecp5/arch.cc
index d72b0085..d2d62241 100644
--- a/ecp5/arch.cc
+++ b/ecp5/arch.cc
@@ -422,7 +422,7 @@ delay_t Arch::predictDelay(const NetInfo *net_info, const PortRef &sink) const
     return 200 * (abs(driver_loc.x - sink_loc.x) + abs(driver_loc.y - sink_loc.y));
 }
 
-delay_t Arch::getBudgetOverride(const NetInfo *net_info, const PortRef &sink, delay_t budget) const { return budget; }
+bool Arch::getBudgetOverride(const NetInfo *net_info, const PortRef &sink, delay_t &budget) const { return false; }
 
 // -----------------------------------------------------------------------
 
diff --git a/ecp5/arch.h b/ecp5/arch.h
index 74f0c4e1..e00e111a 100644
--- a/ecp5/arch.h
+++ b/ecp5/arch.h
@@ -805,7 +805,7 @@ struct Arch : BaseCtx
     delay_t getRipupDelayPenalty() const { return 200; }
     float getDelayNS(delay_t v) const { return v * 0.001; }
     uint32_t getDelayChecksum(delay_t v) const { return v; }
-    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;
 
     // -------------------------------------------------
 
diff --git a/generic/arch.cc b/generic/arch.cc
index 7e65d411..0fa93da8 100644
--- a/generic/arch.cc
+++ b/generic/arch.cc
@@ -408,7 +408,7 @@ delay_t Arch::predictDelay(const NetInfo *net_info, const PortRef &sink) const
     return (dx + dy) * grid_distance_to_delay;
 }
 
-delay_t Arch::getBudgetOverride(const NetInfo *net_info, const PortRef &sink, delay_t budget) const { return budget; }
+bool Arch::getBudgetOverride(const NetInfo *net_info, const PortRef &sink, delay_t &budget) const { return false; }
 
 // ---------------------------------------------------------------
 
diff --git a/generic/arch.h b/generic/arch.h
index a5b3470f..59fe8d05 100644
--- a/generic/arch.h
+++ b/generic/arch.h
@@ -200,7 +200,7 @@ struct Arch : BaseCtx
     delay_t getRipupDelayPenalty() const { return 1.0; }
     float getDelayNS(delay_t v) const { return v; }
     uint32_t getDelayChecksum(delay_t v) const { return 0; }
-    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;
 
     bool pack() { return true; }
     bool place();
diff --git a/ice40/arch.cc b/ice40/arch.cc
index 0b168383..fcc9d798 100644
--- a/ice40/arch.cc
+++ b/ice40/arch.cc
@@ -637,17 +637,34 @@ std::vector<GroupId> Arch::getGroupGroups(GroupId group) const
 
 // -----------------------------------------------------------------------
 
-delay_t Arch::getBudgetOverride(const NetInfo *net_info, const PortRef &sink, delay_t budget) 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)
-            return 0;
-        return 250;
+            budget = 0;
+        else switch (args.type) {
+#ifndef ICE40_HX1K_ONLY
+            case ArchArgs::HX8K:
+#endif
+            case ArchArgs::HX1K:
+                budget = 190; break;
+#ifndef ICE40_HX1K_ONLY
+            case ArchArgs::LP384:
+            case ArchArgs::LP1K:
+            case ArchArgs::LP8K:
+                budget = 290; break;
+            case ArchArgs::UP5K:
+                budget = 560; break;
+#endif
+            default:
+                log_error("Unsupported iCE40 chip type.\n");
+        }
+        return true;
     }
-    return budget;
+    return false;
 }
 
 // -----------------------------------------------------------------------
diff --git a/ice40/arch.h b/ice40/arch.h
index 236f73f1..328950df 100644
--- a/ice40/arch.h
+++ b/ice40/arch.h
@@ -766,7 +766,7 @@ struct Arch : BaseCtx
     delay_t getRipupDelayPenalty() const { return 200; }
     float getDelayNS(delay_t v) const { return v * 0.001; }
     uint32_t getDelayChecksum(delay_t v) const { return v; }
-    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;
 
     // -------------------------------------------------