Add --max-replication option (#7139)

bin/verilator

@@ -482,6 +482,7 @@ detailed descriptions of these arguments.
     --quiet-stats               Don't print statistics
     --relative-includes         Resolve includes relative to current file
     --reloop-limit <value>      Minimum iterations for forming loops
+    --replication-limit <value> Replication concatenation limit (default: 8k)
     --report-unoptflat          Extra diagnostics for UNOPTFLAT
     --rr                        Run Verilator and record with rr
     --runtime-debug             Enable model runtime debugging

docs/guide/exe_verilator.rst

@@ -1516,6 +1516,14 @@ Summary:
    improve C++ compilation time on designs where these sequences are
    common; however, the effect on model performance requires benchmarking.
 
+.. option:: --replication-limit <value>
+
+   Set the limit for replication concatenation (e.g. {1024{1'b1}}). Also applies
+   to unsized literals (e.g. '0).
+
+   This option is on by default with a value of 8k. To disable, pass with a
+   value of 0.
+
 .. option:: --report-unoptflat
 
    Enable extra diagnostics for :option:`UNOPTFLAT` warnings. This

src/V3Number.cpp

@@ -1532,8 +1532,9 @@ V3Number& V3Number::opRepl(const V3Number& lhs,
     // i op repl, L(i)*value(rhs) bit return
     NUM_ASSERT_OP_ARGS1(lhs);
     NUM_ASSERT_LOGIC_ARGS1(lhs);
-    if (rhsval > 8192) {
-        v3warn(WIDTHCONCAT, "More than a 8k bit replication is probably wrong: " << rhsval);
+    if (v3Global.opt.replicationLimit() && rhsval > (uint32_t)v3Global.opt.replicationLimit()) {
+        v3warn(WIDTHCONCAT, "Replication of more that --replication-limit "
+                                << v3Global.opt.replicationLimit() << " is suspect: " << rhsval);
     }
     setZero();
     int obit = 0;

src/V3Options.cpp

@@ -1700,6 +1700,10 @@ void V3Options::parseOptsList(FileLine* fl, const string& optdir, int argc,
         if (m_reloopLimit < 2) fl->v3error("--reloop-limit must be >= 2: " << valp);
     });
     DECL_OPTION("-report-unoptflat", OnOff, &m_reportUnoptflat);
+    DECL_OPTION("-replication-limit", CbVal, [this, fl](const char* valp) {
+        m_replicationLimit = std::atoi(valp);
+        if (m_replicationLimit < 0) fl->v3error("--replication-limit must be >= 0: " << valp);
+    });
     DECL_OPTION("-rr", CbCall, []() {});  // Processed only in bin/verilator shell
     DECL_OPTION("-runtime-debug", CbCall, [this, fl]() {
         decorations(fl, "node");

src/V3Options.h

@@ -338,6 +338,7 @@ private:
     int         m_preprocTokenLimit = 40000; // main switch: --preproc-token-limit
     int         m_publicDepth = 0;   // main switch: --public-depth
     int         m_reloopLimit = 40; // main switch: --reloop-limit
+    int         m_replicationLimit = 8192; // main switch: --replication-limit
     VOptionBool m_skipIdentical;  // main switch: --skip-identical
     bool        m_stopFail = true;  // main switch: --stop-fail
     int         m_threads = 1;      // main switch: --threads
@@ -615,6 +616,7 @@ public:
     int outputGroups() const { return m_outputGroups; }
     int pinsBv() const VL_MT_SAFE { return m_pinsBv; }
     int reloopLimit() const { return m_reloopLimit; }
+    int replicationLimit() const { return m_replicationLimit; }
     VOptionBool skipIdentical() const { return m_skipIdentical; }
     bool stopFail() const { return m_stopFail; }
     int threads() const VL_MT_SAFE { return m_threads; }

test_regress/t/t_concat_large.py

@@ -9,9 +9,9 @@
 
 import vltest_bootstrap
 
-test.scenarios('simulator')
+test.scenarios("simulator")
 
-test.compile()
+test.compile(verilator_flags2=["--Wno-WIDTHCONCAT"])
 
 test.execute()
 

test_regress/t/t_concat_large.v

@@ -9,10 +9,10 @@ module t;
    reg [32767:0] a;
 
    initial begin
-      // verilator lint_off WIDTHCONCAT
       a = {32768{1'b1}};
-      // verilator lint_on WIDTHCONCAT
       if (a[32000] != 1'b1) $stop;
+      a = '0;
+      if (a[32000] != 1'b0) $stop;
       $write("*-* All Finished *-*\n");
       $finish;
    end

test_regress/t/t_concat_large_bad.out

@@ -1,7 +1,11 @@
-%Warning-WIDTHCONCAT: t/t_concat_large_bad.v:9:29: More than a 8k bit replication is probably wrong: 32768
+%Warning-WIDTHCONCAT: t/t_concat_large_bad.v:10:23: Replication of more that --replication-limit 8192 is suspect: 32768
+                                                  : ... note: In instance 't'
+   10 |    wire [32767:0] b = '0;
+      |                       ^~
+                      ... For warning description see https://verilator.org/warn/WIDTHCONCAT?v=latest
+                      ... Use "/* verilator lint_off WIDTHCONCAT */" and lint_on around source to disable this message.
+%Warning-WIDTHCONCAT: t/t_concat_large_bad.v:9:29: Replication of more that --replication-limit 8192 is suspect: 32768
                                                  : ... note: In instance 't'
     9 |    wire [32767:0] a = {32768{1'b1}};
       |                             ^
-                      ... For warning description see https://verilator.org/warn/WIDTHCONCAT?v=latest
-                      ... Use "/* verilator lint_off WIDTHCONCAT */" and lint_on around source to disable this message.
 %Error: Exiting due to

test_regress/t/t_concat_large_bad.v

@@ -7,6 +7,7 @@
 module t;
 
    wire [32767:0] a = {32768{1'b1}};
+   wire [32767:0] b = '0;
 
    initial begin
       $stop;

test_regress/t/t_concat_large_flag.py

@@ -0,0 +1,19 @@
+#!/usr/bin/env python3
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# 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: 2024 Wilson Snyder
+# SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
+
+import vltest_bootstrap
+
+test.scenarios("simulator")
+test.top_filename = "t/t_concat_large.v"
+
+test.compile(verilator_flags2=["--replication-limit 32768"])
+
+test.execute()
+
+test.passes()

test_regress/t/t_concat_large_flag_zero.py

@@ -0,0 +1,19 @@
+#!/usr/bin/env python3
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# 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: 2024 Wilson Snyder
+# SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
+
+import vltest_bootstrap
+
+test.scenarios("simulator")
+test.top_filename = "t/t_concat_large.v"
+
+test.compile(verilator_flags2=["--replication-limit 0"])
+
+test.execute()
+
+test.passes()

test_regress/t/t_flag_values_bad.out

@@ -3,4 +3,5 @@
 %Error: --output-split-ctrace must be >= 0: -1
 %Error: --preproc-token-limit must be > 0: 0
 %Error: --reloop-limit must be >= 2: -1
+%Error: --replication-limit must be >= 0: -1
 %Error: Exiting due to

test_regress/t/t_flag_values_bad.py

@@ -13,7 +13,7 @@ test.scenarios('vlt')
 
 test.lint(verilator_flags2=[
     "--output-split-cfuncs -1", "--output-split-ctrace -1", "--preproc-token-limit 0",
-    "--reloop-limit -1"
+    "--reloop-limit -1", "--replication-limit -1"
 ],
           fails=True,
           expect_filename=test.golden_filename)

test_regress/t/t_func_const3_bad.out

@@ -1,4 +1,4 @@
-%Warning-WIDTHCONCAT: t/t_func_const3_bad.v:12:28: More than a 8k bit replication is probably wrong: 9000
+%Warning-WIDTHCONCAT: t/t_func_const3_bad.v:12:28: Replication of more that --replication-limit 8192 is suspect: 9000
                                                  : ... note: In instance 't.b9k.c9'
    12 |    localparam SOMEP = {BITS{1'b0}};
       |                            ^