Tests: Add test cases for interface array access with loop variable index (#1418 tests) (#7011)

test_regress/t/t_interface_array_loop.py

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+#!/usr/bin/env python3
+# DESCRIPTION: Verilator: Test interface array access with loop variables
+#
+# This program is free software; you can redistribute it and/or modify it
+# under the terms of either the GNU Lesser General Public License Version 3
+# or the Perl Artistic License Version 2.0.
+# SPDX-FileCopyrightText: 2026 Wilson Snyder
+# SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
+
+import vltest_bootstrap
+
+test.scenarios('vlt')
+
+test.compile(fails=True)
+
+test.passes()

test_regress/t/t_interface_array_loop.v

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+// DESCRIPTION: Verilator: Test interface array access with loop variables
+//
+// This file ONLY is placed under the Creative Commons Public Domain.
+// SPDX-FileCopyrightText: 2026 Leela Pakanati
+// SPDX-License-Identifier: CC0-1.0
+
+interface simple_if;
+  logic data;
+  logic [7:0] value;
+
+  modport source (output data, output value);
+  modport sink (input data, input value);
+endinterface
+
+// Test 6: Submodule with interface array as sink modport port
+module sub_sink (
+  simple_if.sink ifaces [3:0],
+  output logic [7:0] sum_out
+);
+  always_comb begin
+    sum_out = 8'b0;
+    for (int i = 0; i < 4; i++) begin
+      sum_out = sum_out + ifaces[i].value;
+    end
+  end
+endmodule
+
+// Test 7: Submodule with interface array as source modport port
+module sub_source (
+  simple_if.source ifaces [3:0]
+);
+  always_comb begin
+    for (int i = 0; i < 4; i++) begin
+      ifaces[i].data = 1'b1;
+      ifaces[i].value = 8'(i + 100);
+    end
+  end
+endmodule
+
+// Test 8: Submodule with interface array without modport
+module sub_generic (
+  simple_if ifaces [3:0]
+);
+  always_comb begin
+    for (int i = 0; i < 4; i++) begin
+      ifaces[i].data = 1'b0;
+      ifaces[i].value = 8'(i + 50);
+    end
+  end
+endmodule
+
+// Test 11: Parameterized submodule with interface array size from parameter
+module l1_param_sub #(
+  parameter NUM_IFACES = 4
+) (
+  simple_if.sink l0_ifaces [NUM_IFACES-1:0],
+  output logic [7:0] l0_sum
+);
+  always_comb begin
+    l0_sum = 8'b0;
+    for (int i = 0; i < NUM_IFACES; i++) begin
+      l0_sum = l0_sum + l0_ifaces[i].value;
+    end
+  end
+endmodule
+
+module t (/*AUTOARG*/
+  // Inputs
+  clk
+);
+
+  input clk;
+
+  localparam N = 4;
+
+  simple_if ifaces [N-1:0] ();
+
+  // Test 1: Simple for loop writing to interface array
+  always_comb begin
+    for (int i = 0; i < N; i++) begin
+      ifaces[i].data = '0;
+    end
+  end
+
+  // Test 2: For loop reading from interface array
+  logic [N-1:0] read_data;
+  always_comb begin
+    for (int j = 0; j < N; j++) begin
+      read_data[j] = ifaces[j].data;
+    end
+  end
+
+  // Test 3: For loop with expression in body
+  always_comb begin
+    for (int k = 0; k < N-1; k++) begin
+      // Use k to index, accessing different member
+      ifaces[k].value = 8'(k);
+    end
+    ifaces[N-1].value = 8'hFF;
+  end
+
+  // Test 4: Descending loop with >= comparison
+  logic [N-1:0] desc_data;
+  always_comb begin
+    for (int p = N-1; p >= 0; p--) begin
+      desc_data[p] = ifaces[p].data;
+    end
+  end
+
+  // Test 4b: Ascending loop with <= comparison
+  logic [N-1:0] lte_data;
+  always_comb begin
+    for (int m = 0; m <= N-1; m++) begin
+      lte_data[m] = ifaces[m].data;
+    end
+  end
+
+  // Test 4c: Descending loop with > comparison
+  simple_if gt_ifaces [N-1:0] ();
+  always_comb begin
+    for (int n = N; n > 0; n--) begin
+      gt_ifaces[n-1].data = 1'b1;
+      gt_ifaces[n-1].value = 8'(n);
+    end
+  end
+
+  // Test 5: Multiple interface arrays in same loop
+  simple_if other_ifaces [N-1:0] ();
+  always_comb begin
+    for (int q = 0; q < N; q++) begin
+      other_ifaces[q].data = ifaces[q].data;
+      other_ifaces[q].value = ifaces[q].value;
+    end
+  end
+
+  // Test 6: Interface array as sink modport port (read from ports in loop)
+  logic [7:0] sink_sum;
+  sub_sink u_sub_sink (.ifaces(ifaces), .sum_out(sink_sum));
+
+  // Test 7: Interface array as source modport port (write to ports in loop)
+  simple_if source_ifaces [N-1:0] ();
+  sub_source u_sub_source (.ifaces(source_ifaces));
+
+  // Test 8: Interface array without modport (read/write in loop)
+  simple_if generic_ifaces [N-1:0] ();
+  sub_generic u_sub_generic (.ifaces(generic_ifaces));
+
+  // Test 9: Ascending loop with step of 2
+  simple_if step2_ifaces [7:0] ();
+  always_comb begin
+    for (int i = 0; i < 8; i += 2) begin
+      step2_ifaces[i].data = 1'b1;
+      step2_ifaces[i].value = 8'(i);
+    end
+    for (int i = 1; i < 8; i += 2) begin
+      step2_ifaces[i].data = 1'b0;
+      step2_ifaces[i].value = 8'hAA;
+    end
+  end
+
+  // Test 10: Descending loop with step of -2
+  simple_if step2d_ifaces [7:0] ();
+  always_comb begin
+    for (int i = 6; i >= 0; i -= 2) begin
+      step2d_ifaces[i].data = 1'b1;
+      step2d_ifaces[i].value = 8'(i);
+    end
+    for (int i = 7; i >= 1; i -= 2) begin
+      step2d_ifaces[i].data = 1'b0;
+      step2d_ifaces[i].value = 8'hBB;
+    end
+  end
+
+  // Test 11: Parameterized submodule with interface array size from parameter
+  // Override NUM_IFACES from default 4 to 6 to test that pre-unroll
+  // uses the overridden parameter value (not the default)
+  simple_if l0_param_ifaces [5:0] ();
+  always_comb begin
+    for (int i = 0; i < 6; i++) begin
+      l0_param_ifaces[i].data = 1'b1;
+      l0_param_ifaces[i].value = 8'(i * 10);
+    end
+  end
+  logic [7:0] l0_param_sum;
+  l1_param_sub #(.NUM_IFACES(6)) u_l1_param (
+    .l0_ifaces(l0_param_ifaces),
+    .l0_sum(l0_param_sum)
+  );
+
+  // Test 12: Complex index expression (N-1-i) - reversed assignment
+  simple_if rev_ifaces [N-1:0] ();
+  always_comb begin
+    for (int i = 0; i < N; i++) begin
+      rev_ifaces[N-1-i].data = 1'b1;
+      rev_ifaces[N-1-i].value = 8'(i);
+    end
+  end
+
+  // Test 13: Non-zero-based interface array range [2:5]
+  simple_if nzb_ifaces [2:5] ();
+  always_comb begin
+    for (int i = 2; i <= 5; i++) begin
+      nzb_ifaces[i].data = 1'b1;
+      nzb_ifaces[i].value = 8'(i);
+    end
+  end
+
+  // Verification
+  int cycle;
+  initial cycle = 0;
+
+  always @(posedge clk) begin
+    cycle <= cycle + 1;
+
+    // Check that interfaces were properly accessed
+    if (cycle == 1) begin
+      // After initialization, data should be 0
+      for (int i = 0; i < N; i++) begin
+        if (ifaces[i].data !== 1'b0) begin
+          $display("%%Error: ifaces[%0d].data should be 0, got %b", i, ifaces[i].data);
+          $stop;
+        end
+      end
+
+      // Check values
+      for (int i = 0; i < N-1; i++) begin
+        if (ifaces[i].value !== 8'(i)) begin
+          $display("%%Error: ifaces[%0d].value should be %0d, got %0d", i, i, ifaces[i].value);
+          $stop;
+        end
+      end
+      if (ifaces[N-1].value !== 8'hFF) begin
+        $display("%%Error: ifaces[%0d].value should be 0xFF, got %0d", N-1, ifaces[N-1].value);
+        $stop;
+      end
+
+      // Test 4b: Check lte_data (uses <= comparison)
+      for (int i = 0; i < N; i++) begin
+        if (lte_data[i] !== 1'b0) begin
+          $display("%%Error: lte_data[%0d] should be 0, got %b", i, lte_data[i]);
+          $stop;
+        end
+      end
+
+      // Test 4c: Check gt_ifaces (uses > comparison, values are 1,2,3,4)
+      for (int i = 0; i < N; i++) begin
+        if (gt_ifaces[i].data !== 1'b1) begin
+          $display("%%Error: gt_ifaces[%0d].data should be 1, got %b", i, gt_ifaces[i].data);
+          $stop;
+        end
+        if (gt_ifaces[i].value !== 8'(i + 1)) begin
+          $display("%%Error: gt_ifaces[%0d].value should be %0d, got %0d", i, i+1, gt_ifaces[i].value);
+          $stop;
+        end
+      end
+
+      // Test 6: Check sink_sum (sum of ifaces[0..3].value = 0+1+2+255 = 258 = 0x02)
+      if (sink_sum !== 8'h02) begin
+        $display("%%Error: sink_sum should be 0x02, got 0x%02x", sink_sum);
+        $stop;
+      end
+
+      // Test 7: Check source_ifaces (written by sub_source with i+100)
+      for (int i = 0; i < N; i++) begin
+        if (source_ifaces[i].data !== 1'b1) begin
+          $display("%%Error: source_ifaces[%0d].data should be 1, got %b", i, source_ifaces[i].data);
+          $stop;
+        end
+        if (source_ifaces[i].value !== 8'(i + 100)) begin
+          $display("%%Error: source_ifaces[%0d].value should be %0d, got %0d", i, i+100, source_ifaces[i].value);
+          $stop;
+        end
+      end
+
+      // Test 8: Check generic_ifaces (written by sub_generic with i+50)
+      for (int i = 0; i < N; i++) begin
+        if (generic_ifaces[i].data !== 1'b0) begin
+          $display("%%Error: generic_ifaces[%0d].data should be 0, got %b", i, generic_ifaces[i].data);
+          $stop;
+        end
+        if (generic_ifaces[i].value !== 8'(i + 50)) begin
+          $display("%%Error: generic_ifaces[%0d].value should be %0d, got %0d", i, i+50, generic_ifaces[i].value);
+          $stop;
+        end
+      end
+
+      // Test 9: Check step2_ifaces (even indices have i, odd have 0xAA)
+      for (int i = 0; i < 8; i++) begin
+        if (i % 2 == 0) begin
+          if (step2_ifaces[i].data !== 1'b1) begin
+            $display("%%Error: step2_ifaces[%0d].data should be 1, got %b", i, step2_ifaces[i].data);
+            $stop;
+          end
+          if (step2_ifaces[i].value !== 8'(i)) begin
+            $display("%%Error: step2_ifaces[%0d].value should be %0d, got %0d", i, i, step2_ifaces[i].value);
+            $stop;
+          end
+        end else begin
+          if (step2_ifaces[i].data !== 1'b0) begin
+            $display("%%Error: step2_ifaces[%0d].data should be 0, got %b", i, step2_ifaces[i].data);
+            $stop;
+          end
+          if (step2_ifaces[i].value !== 8'hAA) begin
+            $display("%%Error: step2_ifaces[%0d].value should be 0xAA, got 0x%02x", i, step2_ifaces[i].value);
+            $stop;
+          end
+        end
+      end
+
+      // Test 10: Check step2d_ifaces (even indices descending, odd indices 0xBB)
+      for (int i = 0; i < 8; i++) begin
+        if (i % 2 == 0) begin
+          if (step2d_ifaces[i].data !== 1'b1) begin
+            $display("%%Error: step2d_ifaces[%0d].data should be 1, got %b", i, step2d_ifaces[i].data);
+            $stop;
+          end
+          if (step2d_ifaces[i].value !== 8'(i)) begin
+            $display("%%Error: step2d_ifaces[%0d].value should be %0d, got %0d", i, i, step2d_ifaces[i].value);
+            $stop;
+          end
+        end else begin
+          if (step2d_ifaces[i].data !== 1'b0) begin
+            $display("%%Error: step2d_ifaces[%0d].data should be 0, got %b", i, step2d_ifaces[i].data);
+            $stop;
+          end
+          if (step2d_ifaces[i].value !== 8'hBB) begin
+            $display("%%Error: step2d_ifaces[%0d].value should be 0xBB, got 0x%02x", i, step2d_ifaces[i].value);
+            $stop;
+          end
+        end
+      end
+
+      // Test 11: Check l0_param_sum (0*10 + 1*10 + 2*10 + 3*10 + 4*10 + 5*10 = 150)
+      if (l0_param_sum !== 8'd150) begin
+        $display("%%Error: l0_param_sum should be 150, got %0d", l0_param_sum);
+        $stop;
+      end
+
+      // Test 12: Check rev_ifaces (reversed: rev_ifaces[N-1-i].value = i)
+      // So rev_ifaces[3].value=0, rev_ifaces[2].value=1, rev_ifaces[1].value=2, rev_ifaces[0].value=3
+      for (int i = 0; i < N; i++) begin
+        if (rev_ifaces[i].data !== 1'b1) begin
+          $display("%%Error: rev_ifaces[%0d].data should be 1, got %b", i, rev_ifaces[i].data);
+          $stop;
+        end
+        if (rev_ifaces[i].value !== 8'(N - 1 - i)) begin
+          $display("%%Error: rev_ifaces[%0d].value should be %0d, got %0d", i, N-1-i, rev_ifaces[i].value);
+          $stop;
+        end
+      end
+
+      // Test 13: Check nzb_ifaces (non-zero-based [2:5], nzb_ifaces[i].value = i)
+      for (int i = 2; i <= 5; i++) begin
+        if (nzb_ifaces[i].data !== 1'b1) begin
+          $display("%%Error: nzb_ifaces[%0d].data should be 1, got %b", i, nzb_ifaces[i].data);
+          $stop;
+        end
+        if (nzb_ifaces[i].value !== 8'(i)) begin
+          $display("%%Error: nzb_ifaces[%0d].value should be %0d, got %0d", i, i, nzb_ifaces[i].value);
+          $stop;
+        end
+      end
+    end
+
+    if (cycle == 5) begin
+      $write("*-* All Finished *-*\n");
+      $finish;
+    end
+  end
+
+endmodule

test_regress/t/t_interface_array_loop_bad.out

@@ -0,0 +1,10 @@
+%Error: t/t_interface_array_loop_bad.v:27:14: Expecting expression to be constant, but variable isn't const: 'i'
+                                            : ... note: In instance 't'
+   27 |       ifaces[i].value = 8'(i);
+      |              ^
+        ... See the manual at https://verilator.org/verilator_doc.html?v=latest for more assistance.
+%Error: t/t_interface_array_loop_bad.v:27:13: Could not expand constant selection inside dotted reference: 'i'
+                                            : ... note: In instance 't'
+   27 |       ifaces[i].value = 8'(i);
+      |             ^
+%Error: Exiting due to

test_regress/t/t_interface_array_loop_bad.py

@@ -0,0 +1,16 @@
+#!/usr/bin/env python3
+# DESCRIPTION: Verilator: Test non-constant interface array loop index error
+#
+# This program is free software; you can redistribute it and/or modify it
+# under the terms of either the GNU Lesser General Public License Version 3
+# or the Perl Artistic License Version 2.0.
+# SPDX-FileCopyrightText: 2026 Wilson Snyder
+# SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
+
+import vltest_bootstrap
+
+test.scenarios('linter')
+
+test.lint(fails=True, expect_filename=test.golden_filename)
+
+test.passes()

test_regress/t/t_interface_array_loop_bad.v

@@ -0,0 +1,36 @@
+// DESCRIPTION: Verilator: Test non-constant interface array loop index error
+//
+// This file ONLY is placed under the Creative Commons Public Domain.
+// SPDX-FileCopyrightText: 2026 Leela Pakanati
+// SPDX-License-Identifier: CC0-1.0
+
+interface simple_bad_if;
+  logic [7:0] value;
+endinterface
+
+module t (/*AUTOARG*/
+  // Inputs
+  clk
+);
+
+  input clk;
+
+  localparam N = 4;
+
+  simple_bad_if ifaces [N-1:0] ();
+
+  // BAD: Loop with runtime-variable bound - not unrollable, so the
+  // interface array index cannot be resolved to a constant.
+  logic [7:0] limit;
+  always_comb begin
+    for (int i = 0; i < limit; i++) begin
+      ifaces[i].value = 8'(i);
+    end
+  end
+
+  initial begin
+    $write("*-* All Finished *-*\n");
+    $finish;
+  end
+
+endmodule

test_regress/t/t_interface_array_loop_noinl.py

@@ -0,0 +1,17 @@
+#!/usr/bin/env python3
+# DESCRIPTION: Verilator: Test interface array access with loop variables (no inline)
+#
+# This program is free software; you can redistribute it and/or modify it
+# under the terms of either the GNU Lesser General Public License Version 3
+# or the Perl Artistic License Version 2.0.
+# SPDX-FileCopyrightText: 2026 Wilson Snyder
+# SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
+
+import vltest_bootstrap
+
+test.scenarios('vlt')
+test.top_filename = "t/t_interface_array_loop.v"
+
+test.compile(fails=True, v_flags2=["-fno-inline"])
+
+test.passes()