verilator/test_regress/t/t_timing_class.v

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Timing support (#3363) Adds timing support to Verilator. It makes it possible to use delays, event controls within processes (not just at the start), wait statements, and forks. Building a design with those constructs requires a compiler that supports C++20 coroutines (GCC 10, Clang 5). The basic idea is to have processes and tasks with delays/event controls implemented as C++20 coroutines. This allows us to suspend and resume them at any time. There are five main runtime classes responsible for managing suspended coroutines: * `VlCoroutineHandle`, a wrapper over C++20's `std::coroutine_handle` with move semantics and automatic cleanup. * `VlDelayScheduler`, for coroutines suspended by delays. It resumes them at a proper simulation time. * `VlTriggerScheduler`, for coroutines suspended by event controls. It resumes them if its corresponding trigger was set. * `VlForkSync`, used for syncing `fork..join` and `fork..join_any` blocks. * `VlCoroutine`, the return type of all verilated coroutines. It allows for suspending a stack of coroutines (normally, C++ coroutines are stackless). There is a new visitor in `V3Timing.cpp` which: * scales delays according to the timescale, * simplifies intra-assignment timing controls and net delays into regular timing controls and assignments, * simplifies wait statements into loops with event controls, * marks processes and tasks with timing controls in them as suspendable, * creates delay, trigger scheduler, and fork sync variables, * transforms timing controls and fork joins into C++ awaits There are new functions in `V3SchedTiming.cpp` (used by `V3Sched.cpp`) that integrate static scheduling with timing. This involves providing external domains for variables, so that the necessary combinational logic gets triggered after coroutine resumption, as well as statements that need to be injected into the design eval function to perform this resumption at the correct time. There is also a function that transforms forked processes into separate functions. See the comments in `verilated_timing.h`, `verilated_timing.cpp`, `V3Timing.cpp`, and `V3SchedTiming.cpp`, as well as the internals documentation for more details. Signed-off-by: Krzysztof Bieganski <kbieganski@antmicro.com>
2022-08-22 12:26:32 +00:00
// DESCRIPTION: Verilator: Verilog Test module
//
// This file ONLY is placed under the Creative Commons Public Domain, for
// any use, without warranty, 2022 by Antmicro Ltd.
// SPDX-License-Identifier: CC0-1.0
`ifdef TEST_VERBOSE
`define WRITE_VERBOSE(args) $write args
`else
`define WRITE_VERBOSE(args)
`endif
module t;
// =============================================
// EVENTS
class EventClass;
event e;
task sleep; /* @e; */ endtask // Unsupported
task wake; ->e; endtask
endclass
EventClass ec = new;
int event_trig_count = 0;
initial begin
@ec.e;
ec.sleep;
end
initial #25 ec.wake;
initial #50 ->ec.e;
always @ec.e begin
event_trig_count++;
`WRITE_VERBOSE(("Event in class triggered at time %0t!\n", $time));
end
// =============================================
// DELAYS
virtual class DelayClass;
pure virtual task do_delay;
pure virtual task do_sth_else;
endclass
`ifdef TEST_VERBOSE
`define DELAY_CLASS(dt) \
class Delay``dt extends DelayClass; \
virtual task do_delay; \
$write("Starting a #%0d delay\n", dt); \
#dt \
$write("Ended a #%0d delay\n", dt); \
endtask \
virtual task do_sth_else; \
$write("Task with no delay (in Delay%0d)\n", dt); \
endtask \
endclass
`else
`define DELAY_CLASS(dt) \
class Delay``dt extends DelayClass; \
virtual task do_delay; \
#dt; \
endtask \
virtual task do_sth_else; \
endtask \
endclass
`endif
`DELAY_CLASS(10);
`DELAY_CLASS(20);
`DELAY_CLASS(40);
class NoDelay extends DelayClass;
virtual task do_delay;
`WRITE_VERBOSE(("Task with no delay\n"));
endtask
virtual task do_sth_else;
`WRITE_VERBOSE(("Task with no delay (in NoDelay)\n"));
endtask
endclass
class AssignDelayClass;
logic x;
logic y;
task do_assign;
y = #10 x;
endtask
endclass
initial begin
DelayClass dc;
Delay10 d10 = new;
Delay20 d20 = new;
Delay40 d40 = new;
NoDelay dNo = new;
AssignDelayClass dAsgn = new;
`WRITE_VERBOSE(("I'm at time %0t\n", $time));
dc = d10;
dc.do_delay;
dc.do_sth_else;
`WRITE_VERBOSE(("I'm at time %0t\n", $time));
if ($time != 10) $stop;
dc = d20;
dc.do_delay;
dc.do_sth_else;
`WRITE_VERBOSE(("I'm at time %0t\n", $time));
if ($time != 30) $stop;
dc = d40;
dc.do_delay;
dc.do_sth_else;
`WRITE_VERBOSE(("I'm at time %0t\n", $time));
if ($time != 70) $stop;
dc = dNo;
dc.do_delay;
dc.do_sth_else;
`WRITE_VERBOSE(("I'm at time %0t\n", $time));
dAsgn.x = 1;
dAsgn.y = 0;
fork #5 dAsgn.x = 0; join_none
dAsgn.do_assign;
if ($time != 80) $stop;
if (event_trig_count != 2) $stop;
if (dAsgn.y != 1) $stop;
$write("*-* All Finished *-*\n");
$finish;
end
// =============================================
// FORKS
class ForkDelayClass;
task do_delay; #40; endtask
endclass
class ForkClass;
int done = 0;
task do_fork();
ForkDelayClass d;
fork
begin
#10 done++;
`WRITE_VERBOSE(("Forked process %0d ending at time %0t\n", done, $time));
end
begin
#20 done++;
`WRITE_VERBOSE(("Forked process %0d ending at time %0t\n", done, $time));
d = new;
end
begin
#30 d.do_delay;
done++;
`WRITE_VERBOSE(("Forked process %0d ending at time %0t\n", done, $time));
end
join
done++;
`WRITE_VERBOSE(("All forked processes ended at time %0t\n", $time));
endtask
endclass
initial begin
ForkClass fc = new;
fc.do_fork;
if (fc.done != 4 || $time != 70) $stop;
end
initial #81 $stop; // timeout
endmodule