Fix CASEINCOMPLETE when covers all enum values (#3745) (#3782).

Co-authored-by: "G-A. Kamendje" <gkamendje@gmail.com>

Changes

@@ -23,6 +23,7 @@ Verilator 5.003 devel
 * Internal AST improvements, also affect XML format (#3721). [Geza Lore]
 * Change ENDLABEL from warning into an error.
 * Deprecate verilated_fst_sc.cpp and verilated_vcd_sc.cpp.
+* Fix CASEINCOMPLETE when covers all enum values (#3745) (#3782). [Guy-Armand Kamendje]
 * Fix return type of $countbits functions to int (#3725). [Ryszard Rozak, Antmicro Ltd]
 * Fix missing UNUSED warnings with --coverage (#3736). [alejandro-castro-ortegon]
 * Fix tracing parameters overridden with -G (#3723). [Iztok Jeras]

docs/CONTRIBUTORS

@@ -36,6 +36,7 @@ Glen Gibb
 Graham Rushton
 Guokai Chen
 Gustav Svensk
+G-A. Kamendje
 Harald Heckmann
 Howard Su
 Huang Rui

docs/guide/warnings.rst

@@ -253,6 +253,12 @@ List Of Warnings
    :code:`default: ;` so that any design assumption violations will be
    discovered in simulation.
 
+   Unique case statements that select on an enumerated variable, where all
+   of the enumerated values are covered by case items, are considered
+   complete even if illegal non-enumerated values are not covered by the
+   case statement.  To check that illegal values are not hit, use
+   :vlopt:`--assert` (see IEEE 1800-2017 12.5.3).
+
    Ignoring this warning will only suppress the lint check, it will
    simulate correctly.
 

src/V3Case.cpp

@@ -139,7 +139,33 @@ private:
     std::array<AstNode*, 1 << CASE_OVERLAP_WIDTH> m_valueItem;
 
     // METHODS
-
+    bool caseIsEnumComplete(AstCase* nodep, uint32_t numCases) {
+        // Return true if case is across an enum, and every value in the case
+        // statement corresponds to one of the enum values
+        if (!nodep->uniquePragma() && !nodep->unique0Pragma()) return false;
+        AstEnumDType* const enumDtp
+            = VN_CAST(nodep->exprp()->dtypep()->skipRefToEnump(), EnumDType);
+        if (!enumDtp) return false;  // Case isn't enum
+        AstBasicDType* const basicp = enumDtp->subDTypep()->basicp();
+        if (!basicp) return false;  // Not simple type (perhaps IEEE illegal)
+        if (basicp->width() > 32) return false;
+        // Find all case values into a set
+        std::set<uint32_t> caseSet;
+        for (uint32_t i = 0; i < numCases; ++i) {  // All case items
+            if (m_valueItem[i]) caseSet.emplace(i);
+        }
+        // Find all enum values into a set
+        std::set<uint32_t> enumSet;
+        for (AstEnumItem* itemp = enumDtp->itemsp(); itemp;
+             itemp = VN_AS(itemp->nextp(), EnumItem)) {
+            AstConst* const econstp = VN_AS(itemp->valuep(), Const);
+            const uint32_t val = econstp->toUInt();
+            // UINFO(9, "Complete enum item " << val << ": " << itemp << endl);
+            enumSet.emplace(val);
+        }
+        // If sets match, all covered
+        return (caseSet == enumSet);
+    }
     bool isCaseTreeFast(AstCase* nodep) {
         int width = 0;
         bool opaque = false;
@@ -227,15 +253,18 @@ private:
                 }
             }
         }
-        for (uint32_t i = 0; i < numCases; ++i) {
-            if (!m_valueItem[i]) {
-                nodep->v3warn(CASEINCOMPLETE, "Case values incompletely covered "
-                                              "(example pattern 0x"
-                                                  << std::hex << i << ")");
-                m_caseNoOverlapsAllCovered = false;
-                return false;
+        if (!caseIsEnumComplete(nodep, numCases)) {
+            for (uint32_t i = 0; i < numCases; ++i) {
+                if (!m_valueItem[i]) {
+                    nodep->v3warn(CASEINCOMPLETE, "Case values incompletely covered "
+                                                  "(example pattern 0x"
+                                                      << std::hex << i << ")");
+                    m_caseNoOverlapsAllCovered = false;
+                    return false;
+                }
             }
         }
+
         if (m_caseItems <= 3
             // Avoid e.g. priority expanders from going crazy in expansion
             || (m_caseWidth >= 8 && (m_caseItems <= (m_caseWidth + 1)))) {

test_regress/t/t_case_enum_complete.pl

@@ -0,0 +1,19 @@
+#!/usr/bin/env perl
+if (!$::Driver) { use FindBin; exec("$FindBin::Bin/bootstrap.pl", @ARGV, $0); die; }
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# Copyright 2003 by Wilson Snyder. 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-License-Identifier: LGPL-3.0-only OR Artistic-2.0
+
+scenarios(linter => 1);
+
+lint(
+    verilator_flags2 => ["--lint-only -Wwarn-CASEINCOMPLETE"],
+    fails => 0,
+    );
+
+ok(1);
+1;

test_regress/t/t_case_enum_complete.v

@@ -0,0 +1,20 @@
+// DESCRIPTION: Verilator: SystemVerilog Test module
+//
+// This file ONLY is placed under the Creative Commons Public Domain, for
+// any use, without warranty, 2022 by Wilson Snyder.
+// SPDX-License-Identifier: CC0-1.0
+
+module t;
+
+   enum logic [2:0] {S0, S1, S2} state;
+
+   initial begin
+      state = S1;
+
+      unique case (state)
+        S0: $stop;
+        S1: $finish;
+        S2: $stop;
+      endcase
+   end
+endmodule

test_regress/t/t_case_enum_incomplete_bad.out

@@ -0,0 +1,6 @@
+%Warning-CASEINCOMPLETE: t/t_case_enum_incomplete_bad.v:14:14: Case values incompletely covered (example pattern 0x1)
+   14 |       unique case (state)
+      |              ^~~~
+                         ... For warning description see https://verilator.org/warn/CASEINCOMPLETE?v=latest
+                         ... Use "/* verilator lint_off CASEINCOMPLETE */" and lint_on around source to disable this message.
+%Error: Exiting due to

test_regress/t/t_case_enum_incomplete_bad.pl

@@ -0,0 +1,20 @@
+#!/usr/bin/env perl
+if (!$::Driver) { use FindBin; exec("$FindBin::Bin/bootstrap.pl", @ARGV, $0); die; }
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# Copyright 2022 by Wilson Snyder. 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-License-Identifier: LGPL-3.0-only OR Artistic-2.0
+
+scenarios(linter => 1);
+
+lint(
+    verilator_flags2 => ['--assert'],
+    fails => 1,
+    expect_filename => $Self->{golden_filename},
+    );
+
+ok(1);
+1;

test_regress/t/t_case_enum_incomplete_bad.v

@@ -0,0 +1,19 @@
+// DESCRIPTION: Verilator: SystemVerilog Test module
+//
+// This file ONLY is placed under the Creative Commons Public Domain, for
+// any use, without warranty, 2022 by Wilson Snyder.
+// SPDX-License-Identifier: CC0-1.0
+
+module t;
+
+   enum logic [2:0] {S0, S1, S2} state;
+
+   initial begin
+      state = S1;
+
+      unique case (state)
+        S0: $stop;
+        S2: $stop;
+      endcase
+   end
+endmodule