cyclonev: More validity checking thoughts

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

cyclonev/arch.cc

@@ -308,6 +308,19 @@ void Arch::add_bel_pin(BelId bel, IdString pin, PortType dir, WireId wire)
     wires[wire].bel_pins.push_back(bel_pin);
 }
 
+void Arch::assign_default_pinmap(CellInfo *cell)
+{
+    for (auto &port : cell->ports) {
+        auto &pinmap = cell->pin_data[port.first].bel_pins;
+        if (!pinmap.empty())
+            continue; // already mapped
+        if (is_comb_cell(cell->type) && comb_pinmap.count(port.first))
+            pinmap.push_back(comb_pinmap.at(port.first)); // default comb mapping for placer purposes
+        else
+            pinmap.push_back(port.first); // default: assume bel pin named the same as cell pin
+    }
+}
+
 #ifdef WITH_HEAP
 const std::string Arch::defaultPlacer = "heap";
 #else

cyclonev/arch.h

@@ -393,6 +393,11 @@ struct Arch : BaseArch<ArchRanges>
 
     BelInfo &bel_data(BelId bel) { return bels_by_tile.at(pos2idx(bel.pos)).at(bel.z); }
     const BelInfo &bel_data(BelId bel) const { return bels_by_tile.at(pos2idx(bel.pos)).at(bel.z); }
+
+    // -------------------------------------------------
+
+    void assign_default_pinmap(CellInfo *cell);
+    static const std::unordered_map<IdString, IdString> comb_pinmap;
 };
 
 NEXTPNR_NAMESPACE_END

cyclonev/archdefs.h

@@ -124,10 +124,19 @@ struct ArchNetInfo
 {
 };
 
+enum CellPinState
+{
+    PIN_SIG = 0,
+    PIN_0 = 1,
+    PIN_1 = 2,
+    PIN_INV = 3,
+};
+
 struct ArchPinInfo
 {
-    // An inverter (INV) has been pushed onto this signal
+    // Used to represent signals that are either tied to implicit constants (rather than explicitly routed constants);
-    bool inverted;
+    // or are inverted
+    CellPinState state = PIN_SIG;
     // The physical bel pins that this logical pin maps to
     std::vector<IdString> bel_pins;
 };
@@ -167,6 +176,7 @@ struct ArchCellInfo
             const NetInfo *comb_out;
 
             int lut_input_count;
+            int used_lut_input_count; // excluding those null/constant
             int lut_bits_count;
 
             bool is_carry, is_shared, is_extended;

cyclonev/constids.inc

@@ -55,6 +55,7 @@ X(MISTRAL_ALUT4)
 X(MISTRAL_ALUT3)
 X(MISTRAL_ALUT2)
 X(MISTRAL_NOT)
+X(MISTRAL_BUF)
 X(MISTRAL_CONST)
 X(MISTRAL_ALUT_ARITH)
 

cyclonev/lab.cc

@@ -195,7 +195,7 @@ ControlSig get_ctrlsig(const CellInfo *cell, IdString port)
     ControlSig result;
     result.net = get_net_or_empty(cell, port);
     if (cell->pin_data.count(port))
-        result.inverted = cell->pin_data.at(port).inverted;
+        result.inverted = cell->pin_data.at(port).state == PIN_INV;
     else
         result.inverted = false;
     return result;
@@ -259,7 +259,8 @@ void Arch::assign_comb_info(CellInfo *cell) const
             ++cell->combInfo.lut_input_count;
             cell->combInfo.lut_in[1] = get_net_or_empty(cell, id_B);
             [[fallthrough]];
-        case ID_MISTRAL_NOT:
+        case ID_MISTRAL_BUF: // used to route through to FFs etc
+        case ID_MISTRAL_NOT: // used for inverters that map to LUTs
             ++cell->combInfo.lut_input_count;
             cell->combInfo.lut_in[0] = get_net_or_empty(cell, id_A);
             [[fallthrough]];
@@ -272,6 +273,10 @@ void Arch::assign_comb_info(CellInfo *cell) const
         // Note that this relationship won't hold for extended mode, when that is supported
         cell->combInfo.lut_bits_count = (1 << cell->combInfo.lut_input_count);
     }
+    cell->combInfo.used_lut_input_count = 0;
+    for (int i = 0; i < cell->combInfo.lut_input_count; i++)
+        if (cell->combInfo.lut_in[i])
+            ++cell->combInfo.used_lut_input_count;
 }
 
 void Arch::assign_ff_info(CellInfo *cell) const
@@ -336,9 +341,9 @@ bool Arch::is_alm_legal(uint32_t lab, uint8_t alm) const
         // There are two ways to route from the fabric into FF data - either routing through a LUT or using the E/F
         // signals and SLOAD=1 (*PKREF*)
         bool route_thru_lut_avail = !luts[i] && (total_lut_inputs < 8) && (used_lut_bits < 64);
-        // E/F is available if the LUT is using less than 6 inputs - TODO: is this correct considering all possible LUT
+        // E/F is available if this LUT is using 3 or fewer inputs - this is conservative and sharing can probably
-        // sharing
+        // improve this situation
-        bool ef_available = (!luts[i] || luts[i]->combInfo.lut_input_count < 6);
+        bool ef_available = (!luts[i] || luts[i]->combInfo.used_lut_input_count <= 3);
         // Control set checking
         bool found_ff = false;
 
@@ -383,4 +388,12 @@ bool Arch::is_lab_ctrlset_legal(uint32_t lab) const
     return true;
 }
 
+// This default cell-bel pin mapping is used to provide estimates during placement only. It will have errors and
+// overlaps and a correct mapping will be resolved twixt placement and routing
+const std::unordered_map<IdString, IdString> Arch::comb_pinmap = {
+        {id_A, id_F0}, // fastest input first
+        {id_B, id_E0}, {id_C, id_D}, {id_D, id_C},       {id_D0, id_C},       {id_D1, id_B},
+        {id_E, id_B},  {id_F, id_A}, {id_Q, id_COMBOUT}, {id_SO, id_COMBOUT},
+};
+
 NEXTPNR_NAMESPACE_END