Add --verilate-jobs option (#3889)

Currently this option isn't used, but in the future it will be used to specify parallelization of Verilation step.

bin/verilator

@@ -362,7 +362,7 @@ detailed descriptions of these arguments.
      +incdir+<dir>              Directory to search for includes
     --inline-mult <value>       Tune module inlining
     --instr-count-dpi <value>   Assumed dynamic instruction count of DPI imports
-     -j <jobs>                  Parallelism for --build (alias to --build-jobs)
+     -j <jobs>                  Parallelism for --build-jobs/--verilate-jobs
     --l2-name <value>           Verilog scope name of the top module
     --language <lang>           Default language standard to parse
      -LDFLAGS <flags>           Linker pre-object arguments for makefile
@@ -445,6 +445,7 @@ detailed descriptions of these arguments.
     --unused-regexp <regexp>    Tune UNUSED lint signals
      -V                         Verbose version and config
      -v <filename>              Verilog library
+    --verilate-jobs             Job threads for Verilation stage
     --no-verilate               Skip Verilation and just compile previously Verilated code
      +verilog1995ext+<ext>      Synonym for +1364-1995ext+<ext>
      +verilog2001ext+<ext>      Synonym for +1364-2001ext+<ext>

docs/guide/exe_verilator.rst

@@ -707,9 +707,10 @@ Summary:
 .. option:: -j [<value>]
 
    Specify the level of parallelism for :vlopt:`--build` if
-   :vlopt:`--build-jobs` isn't provided. If zero, uses the number of threads
-   in the current hardware. Otherwise, the <value> must be a positive
-   integer specifying the maximum number of parallel build jobs.
+   :vlopt:`--build-jobs` isn't provided, and the internal compilation steps
+   of Verilator if :vlopt:`--verilate-jobs` isn't provided. If zero, uses
+   the number of threads in the current hardware. Otherwise, must be a
+   positive integer specifying the maximum number of parallel build jobs.
 
 .. option:: --l2-name <value>
 
@@ -1429,6 +1430,15 @@ Summary:
    execute only the build. This can be useful for rebuilding the Verilated code
    produced by a previous invocation of Verilator.
 
+.. option:: --verilate-jobs [<value>]
+
+   Specify the level of parallelism for the internal compilation steps of
+   Verilator. If zero, uses the number of threads in the current hardware.
+   Otherwise, must be a positive integer specifying the maximum number of
+   parallel build jobs.
+
+   See also :vlopt:`-j`.
+
 .. option:: +verilog1995ext+<ext>
 
    Synonym for :vlopt:`+1364-1995ext+\<ext\>`.

src/V3Options.cpp

@@ -1505,6 +1505,17 @@ void V3Options::parseOptsList(FileLine* fl, const string& optdir, int argc, char
     DECL_OPTION("-v", CbVal, [this, &optdir](const char* valp) {
         V3Options::addLibraryFile(parseFileArg(optdir, valp));
     });
+    DECL_OPTION("-verilate-jobs", CbVal, [this, fl](const char* valp) {
+        int val = std::atoi(valp);
+        if (val < 0) {
+            fl->v3error("--verilate-jobs requires a non-negative integer, but '"
+                        << valp << "' was passed");
+            val = 1;
+        } else if (val == 0) {
+            val = std::thread::hardware_concurrency();
+        }
+        m_verilateJobs = val;
+    });
     DECL_OPTION("-verilate", OnOff, &m_verilate);
     DECL_OPTION("-version", CbCall, [this]() {
         showVersion(false);
@@ -1628,6 +1639,7 @@ void V3Options::parseOptsList(FileLine* fl, const string& optdir, int argc, char
                 ++i;
             }
             if (m_buildJobs == -1) m_buildJobs = val;
+            if (m_verilateJobs == -1) m_verilateJobs = val;
         } else if (argv[i][0] == '-' || argv[i][0] == '+') {
             const char* argvNoDashp = (argv[i][1] == '-') ? (argv[i] + 2) : (argv[i] + 1);
             if (const int consumed = parser.parse(i, argc, argv)) {
@@ -1660,6 +1672,7 @@ void V3Options::parseOptsList(FileLine* fl, const string& optdir, int argc, char
         }
     }
     if (m_buildJobs == -1) m_buildJobs = 1;
+    if (m_verilateJobs == -1) m_verilateJobs = 1;
 }
 
 //======================================================================

src/V3Options.h

@@ -317,6 +317,7 @@ private:
     int         m_traceThreads = 0; // main switch: --trace-threads
     int         m_unrollCount = 64;  // main switch: --unroll-count
     int         m_unrollStmts = 30000;  // main switch: --unroll-stmts
+    int         m_verilateJobs = -1;  // main switch: --verilate-jobs
 
     int         m_compLimitBlocks = 0;  // compiler selection; number of nested blocks
     int         m_compLimitMembers = 64;  // compiler selection; number of members in struct before make anon array
@@ -544,6 +545,7 @@ public:
     }
     int unrollCount() const { return m_unrollCount; }
     int unrollStmts() const { return m_unrollStmts; }
+    int verilateJobs() const { return m_verilateJobs; }
 
     int compLimitBlocks() const { return m_compLimitBlocks; }
     int compLimitMembers() const { return m_compLimitMembers; }

src/V3StatsReport.cpp

@@ -47,6 +47,7 @@ class StatsReport final {
         os << "  " << V3Options::version() << '\n';
         os << "  Arguments: " << v3Global.opt.allArgsString() << '\n';
         os << "  Build jobs: " << v3Global.opt.buildJobs() << '\n';
+        os << "  Verilate jobs: " << v3Global.opt.verilateJobs() << '\n';
         os << '\n';
     }
 

test_regress/t/t_flag_verilate_threads_bad.out

@@ -0,0 +1,2 @@
+%Error: --verilate-jobs requires a non-negative integer, but '-1' was passed
+%Error: Exiting due to

test_regress/t/t_flag_verilate_threads_bad.pl

@@ -0,0 +1,22 @@
+#!/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(vlt => 1);
+
+top_filename("t/t_flag_werror.v");
+
+lint(
+    fails => 1,
+    verilator_flags => [qw(--verilate-jobs -1)],
+    expect_filename => $Self->{golden_filename},
+    );
+
+ok(1);
+1;

test_regress/t/t_vthread.pl

@@ -0,0 +1,58 @@
+#!/usr/bin/env perl
+if (!$::Driver) { use FindBin; exec("$FindBin::Bin/bootstrap.pl", @ARGV, $0); die; }
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# Copyright 2023 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
+use IO::File;
+
+scenarios(vlt => 1);
+
+sub gen {
+    my $filename = shift;
+    my $n = shift;
+
+    my $fh = IO::File->new(">$filename");
+    $fh->print("// Generated by t_vthread.pl\n");
+    $fh->print("module genmod #(int val = 0)(clk, o);\n");
+    $fh->print("  input clk;\n");
+    $fh->print("  output int o;\n");
+    $fh->print("  always @ (posedge clk) begin\n");
+    $fh->print("    o <= val;\n");
+    $fh->print("  end\n");
+    $fh->print("endmodule\n");
+    $fh->print("module t (clk, o);\n");
+    $fh->print("  input clk;\n");
+    $fh->print("  output int o;\n");
+    for (my $i = 0; $i < ($n + 1); ++$i) {
+        $fh->print("  int r$i;\n");
+        $fh->print("  genmod #(.val($i)) rm$i (.clk(clk), .o(r$i));\n");
+    }
+    $fh->print("  always @ (posedge clk) begin\n");
+    $fh->print("    o <= r$n;\n");
+    $fh->print('    $write("*-* All Finished *-*\n");', "\n");
+    $fh->print('    $finish;', "\n");
+    $fh->print("  end\n");
+    $fh->print("endmodule\n");
+}
+
+top_filename("$Self->{obj_dir}/t_vthread.v");
+
+gen($Self->{top_filename}, 6000);
+
+compile(
+    # use --trace to generate trace files that can be parallelized
+    verilator_flags2=>["--stats --trace --verilate-jobs 2"],
+    );
+
+execute(
+    check_finished => 1,
+    );
+
+file_grep($Self->{stats}, qr/Verilate jobs: 2/);
+
+ok(1);
+1;