fix struct member accesses within field select bounds (#330)

CHANGELOG.md

@@ -6,6 +6,11 @@
 * Added support for `bufif0`, `bufif1`, `notif0`, `notif1`, `cmos`, `rcmos`,
   `nmos`, `pmos`, `rnmos`, and `rpmos`.
 
+### Bug Fixes
+
+* Fixed conversion of struct field accesses when the struct's field widths
+  depend on a member of a struct-typed parameter
+
 ### Other Enhancements
 
 * `always_comb` blocks with sensitivities inherited from called functions or

src/Convert/Struct.hs

@@ -385,10 +385,12 @@ convertSubExpr scopes (Dot e x) =
     where
         (subExprType, e') = convertSubExpr scopes e
         (isHier, fieldType, bounds, dims) = lookupFieldInfo scopes subExprType e' x
-        base = fst bounds
-        len = rangeSize bounds
+        -- the offset and size are derived from the struct layout, whose field
+        -- widths may contain member accesses that must themselves be lowered
+        (_, base) = convertSubExpr scopes $ fst bounds
+        (_, len) = convertSubExpr scopes $ rangeSize bounds
         undotted = if null dims || rangeSize (head dims) == RawNum 1
-            then Bit e' (fst bounds)
+            then Bit e' base
             else Range e' IndexedMinus (base, len)
         -- retain signedness of fields which would otherwise be lost via the
         -- resulting bit or range selection

test/core/class_paramstruct.sv

@@ -0,0 +1,26 @@
+package P;
+    typedef struct packed { int unsigned a; int unsigned b; } cfg_t;
+    localparam cfg_t cfg = '{a: 8, b: 4};
+    typedef enum logic [1:0] { S_A, S_B } enum_e;
+endpackage
+
+class C #(parameter P::cfg_t cfg = P::cfg);
+    typedef logic [$clog2(cfg.a) - 1:0] x_t;
+    typedef logic [cfg.b - 1:0] y_t;
+    typedef struct packed { P::enum_e e; x_t x; y_t y; } s_t;
+endclass
+
+module child #(
+    parameter P::cfg_t cfg = P::cfg,
+    parameter type s_t = C#(cfg)::s_t,
+    localparam type x_t = C#(cfg)::x_t
+) (
+    input s_t ins,
+    output x_t out
+);
+    always_comb
+        unique case (ins.e)
+            P::S_A: out = ins.x;
+            default: out = '0;
+        endcase
+endmodule

test/core/class_paramstruct.v

@@ -0,0 +1,11 @@
+module child(
+    input wire [8:0] inp,
+    output reg [2:0] out
+);
+    always @* begin
+        case (inp[8:7])
+            2'd0: out = inp[6:4];
+            default: out = 3'd0;
+        endcase
+    end
+endmodule

test/core/class_paramstruct_tb.v

@@ -0,0 +1,11 @@
+module top;
+    reg [8:0] inp;
+    wire [2:0] out;
+    child c(inp, out);
+    initial begin
+        $monitor("%2d %b %b", $time, inp, out);
+        inp = 9'b00_101_0000; #1;
+        inp = 9'b00_010_1111; #1;
+        inp = 9'b01_111_0000; #1;
+    end
+endmodule