fabulous: Support for complex flops in PnR

Signed-off-by: gatecat <gatecat@ds0.me>

generic/viaduct/fabulous/constids.inc

@@ -110,5 +110,8 @@ X(VDD)
 X(_CONST0_DRV)
 X(_CONST1_DRV)
 
+X(_CONST0)
+X(_CONST1)
+
 X(_LUT_PERM)
 X(_LUT_PERM_IN)

generic/viaduct/fabulous/fab_cfg.h

@@ -43,8 +43,9 @@ struct ControlSetConfig
     signal can drive for a CLB with 8 FFs and 2 clocks split at halfway, the first entry would be 0x0F and the second
     0xF0
     */
-    std::vector<route_mask_t> routing = {0b11111111}; // default 1 shared between all
+    std::vector<route_mask_t> routing; // default 1 shared between all
     bool have_signal = true;
+    int can_mask = -1;
     bool can_invert = false;
 };
 

generic/viaduct/fabulous/fabulous.cc

@@ -52,6 +52,7 @@ struct FabulousImpl : ViaductAPI
                 log_error("unrecognised fabulous option '%s'\n", a.first.c_str());
         }
     }
+
     ~FabulousImpl(){};
     void init(Context *ctx) override
     {
@@ -64,6 +65,7 @@ struct FabulousImpl : ViaductAPI
         else
             is_new_fab = false;
         log_info("Detected FABulous %s format project.\n", is_new_fab ? "2.0" : "1.0");
+        init_default_ctrlset_cfg();
         // To consider: a faster serialised form of the device data (like bba that other arches use) so we don't have to
         // go through the whole csv parsing malarkey each time
         blk_trk = std::make_unique<BlockTracker>(ctx, cfg);
@@ -76,6 +78,22 @@ struct FabulousImpl : ViaductAPI
         ctx->ripup_penalty = 0.5;
     }
 
+    void init_default_ctrlset_cfg()
+    {
+        // TODO: loading from file or something
+        uint64_t default_routing = (1ULL << (cfg.clb.lc_per_clb * cfg.clb.ff_per_lc)) - 1;
+        auto setup_cfg = [&](ControlSetConfig &ctrl, int mask) {
+            ctrl.routing.clear();
+            ctrl.routing.push_back(default_routing);
+            ctrl.can_mask = mask;
+            ctrl.can_invert = false;
+        };
+
+        setup_cfg(cfg.clb.clk, -1);
+        setup_cfg(cfg.clb.en, 1);
+        setup_cfg(cfg.clb.sr, 0);
+    }
+
     void update_cell_timing(Context *ctx)
     {
         // These timings are not realistic. They just make sure nextpnr does some timing-driven optimisation...
@@ -605,9 +623,9 @@ struct FabulousImpl : ViaductAPI
                 return true;
             bool is_carry = cell_tags.get(lut).comb.carry_used;
             if (is_carry) {
-                // Because you have to make sure you route _something_ to each HA input in this mode (undefined I1/I2 inputs aren't OK)
+                // Because you have to make sure you route _something_ to each HA input in this mode (undefined I1/I2
-                // and you also can't swap I0 because it's fixed internally
+                // inputs aren't OK) and you also can't swap I0 because it's fixed internally LUT permutation in carry
-                // LUT permutation in carry mode is just more trouble than it's worth.
+                // mode is just more trouble than it's worth.
                 return false;
             } else {
                 return true; // TODO: other cases where perm illegal; e.g. LUTRAM

generic/viaduct/fabulous/validity_check.cc

@@ -62,6 +62,10 @@ void CellTagger::assign_for(const Context *ctx, const FabricConfig &cfg, const C
             auto get_ctrlsig = [&](IdString name) {
                 const NetInfo *sig = ci->getPort(name);
                 bool invert = sig && bool_or_default(ci->params, ctx->idf("NEG_%s", name.c_str(ctx)));
+                if (sig && sig->driver.cell && sig->driver.cell->type.in(id__CONST0_DRV, id__CONST1_DRV)) {
+                    return ControlSig(((sig->driver.cell->type == id__CONST1_DRV) ^ invert) ? id__CONST1 : id__CONST0,
+                                      false);
+                }
                 return ControlSig(sig ? sig->name : id___disconnected, invert);
             };
             t.ff.clk = get_ctrlsig(id_CLK);
@@ -132,6 +136,13 @@ bool CLBState::check_validity(const LogicConfig &cfg, const CellTagger &cell_dat
             used_en(cfg.en.routing.size());
     auto check_ctrlsig = [&](unsigned idx, ControlSig actual, const ControlSetConfig &ctrl,
                              SSOArray<ControlSig, 2> &used) {
+        if (ctrl.can_mask != -1) {
+            // Using the per-entry control signal masking
+            if (actual.net == id___disconnected || (actual.net == id__CONST0 && ctrl.can_mask == 0) ||
+                (actual.net == id__CONST1 && ctrl.can_mask == 0)) {
+                return true;
+            }
+        }
         // see if we have an already-matching signal available
         for (unsigned i = 0; i < ctrl.routing.size(); i++) {
             // doesn't route to this pin