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dc5c259069
* Improve tracing performance.
Various tactics used to improve performance of both VCD and FST tracing:
- Both: Change tracing functions to templates to take variable widths as
template parameters. For VCD, subsequently specialize these to the
values used by Verilator. This avoids redundant instructions and hard
to predict branches.
- Both: Check for value changes via direct pointer access into the
previous signal value buffer. This eliminates a lot of simple pointer
arithmetic instructions form the tracing code.
- Both: Verilator provides clean input, no need to mask out used bits.
- VCD: pre-compute identifier codes and use memory copy instead of
re-computing them every time a code is emitted. This saves a lot of
instructions and hard to predict branches. The added D-cache misses
are cheaper than the removed branches/instructions.
- VCD: re-write the routines emitting the changes to be more efficient.
- FST: Use previous signal value buffer the same way as the VCD tracing
code, and only call the FST API when a change is detected.
Performance as measured on SweRV EH1, with the pre-canned CoreMark
benchmark running from DCCM/ICCM, clang 6.0.0, Intel i7-3770 @ 3.40GHz,
and IO to ramdisk:
+--------------+---------------+----------------------+
| VCD | FST | FST separate thread |
| (--trace) | (--trace-fst) | (--trace-fst-thread) |
------------+-----------------------------------------------------+
Before | 30.2 s | 121.1 s | 69.8 s |
============+==============+===============+======================+
After | 24.7 s | 45.7 s | 32.4 s |
------------+--------------+---------------+----------------------+
Speedup | 22 % | 256 % | 215 % |
------------+--------------+---------------+----------------------+
Rel. to VCD | 1 x | 1.85 x | 1.31 x |
------------+--------------+---------------+----------------------+
In addition, FST trace size for the above reduced by 48%.
39 lines
1.3 KiB
Perl
Executable File
39 lines
1.3 KiB
Perl
Executable File
#!/usr/bin/perl
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if (!$::Driver) { use FindBin; exec("$FindBin::Bin/bootstrap.pl", @ARGV, $0); die; }
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# DESCRIPTION: Verilator: Verilog Test driver/expect definition
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#
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# Copyright 2003-2009 by Wilson Snyder. This program is free software; you
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# can redistribute it and/or modify it under the terms of either the GNU
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# Lesser General Public License Version 3 or the Perl Artistic License
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# Version 2.0.
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# SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
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# Same test as t_trace_complex, but exercising the old VCD tracing API
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scenarios(simulator => 1);
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top_filename("t/t_trace_complex.v");
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compile(
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verilator_flags2 => ['--cc --trace -CFLAGS -DVL_TRACE_VCD_OLD_API'],
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);
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execute(
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check_finished => 1,
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);
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file_grep ("$Self->{obj_dir}/simx.vcd", qr/ v_strp /);
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file_grep ("$Self->{obj_dir}/simx.vcd", qr/ v_strp_strp /);
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file_grep ("$Self->{obj_dir}/simx.vcd", qr/ v_arrp /);
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file_grep ("$Self->{obj_dir}/simx.vcd", qr/ v_arrp_arrp /);
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file_grep ("$Self->{obj_dir}/simx.vcd", qr/ v_arrp_strp /);
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file_grep ("$Self->{obj_dir}/simx.vcd", qr/ v_arru\(/);
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file_grep ("$Self->{obj_dir}/simx.vcd", qr/ v_arru_arru\(/);
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file_grep ("$Self->{obj_dir}/simx.vcd", qr/ v_arru_arrp\(/);
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file_grep ("$Self->{obj_dir}/simx.vcd", qr/ v_arru_strp\(/);
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vcd_identical ("$Self->{obj_dir}/simx.vcd", "t/t_trace_complex.out");
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ok(1);
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1;
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