Processes without sync rules correspond to simple decision trees that
directly correspond to `always @*` or `always_comb` blocks in Verilog,
and do not need a warning.
This removes the need to suppress warnings during the RTLIL-to-Verilog
conversion performed by Amaranth.
These were previously not being converted correctly leading to yosys
internal cells being written to my netlist.
Signed-off-by: Ethan Mahintorabi <ethanmoon@google.com>
This change only matters for processes that weren't processed by
`proc_rmdead` for which follow-up cases after a default case are treated
differently in Verilog and RTLIL semantics.
The Verilog grammar does not allow an empty case. Most synthesis tools
are quite permissive about this, but Quartus is not. This causes
problems for amaranth with Quartus (see amaranth-lang/amaranth#931).
We add a new flow graph node type, PRINT_SYNC, as they don't get handled
with regular CELL_EVALs. We could probably move this grouping out of
the dump method.
Uses the regex below to search (using vscode):
^\t\tlog\("(.{10,}(?<!\\n)|.{81,}\\n)"\);
Finds any log messages double indented (which help messages are)
and checks if *either* there are is no newline character at the end,
*or* the number of characters before the newline is more than 80.
Before this commit, zero width sigspecs were dumped as "" (empty
string). Unfortunately, 1364-2005 5.2.3.3 indicates that an empty
string is equivalent to "\0", and is 8 bits wide, so that's wrong.
After this commit, a replication operation with a count of zero is
used instead, which is explicitly permitted per 1364-2005 5.1.14,
and is defined to have size zero. (Its operand has to have a non-zero
size for it to be legal, though.)
PR #1203 has addressed this issue before, but in an incomplete way.
- *_en is split into *_ce (clock enable) and *_aload (async load aka
latch gate enable), so both can be present at once
- has_d is removed
- has_gclk is added (to have a clear marker for $ff)
- d_is_const and val_d leftovers are removed
- async2sync, clk2fflogic, opt_dff are updated to operate correctly on
FFs with async load
This mode will be used whenever read port cannot be handled in the
"extract address register" way, ie. whenever it has enable, reset,
init functionality or (in the future) mixed transparency mask.
There will soon be more (versioned) memory cells, so handle passes that
only care if a cell is memory-related by a simple helper call instead of
a hardcoded list.
This commit only affects translation of RTLIL processes (for which
there is limited support).
Due to the event-driven nature of Verilog, processes like
reg x;
always @*
x <= 1;
may never execute. This can be fixed in SystemVerilog code by using
`always_comb` instead of `always @*`, but in Verilog-2001 the options
are limited. This commit implements the following workaround:
reg init = 0;
reg x;
always @* begin
if (init) begin end
x <= 1;
end
Fixes#2271.
Emil J. Tywoniak
Catherine
Jannis Harder
Ethan Mahintorabi
Martin Povišer
Wanda
Charlotte
KrystalDelusion
Marcelina Kościelnicka
Miodrag Milanovic
Claire Xenia Wolf
N. Engelhardt
Xiretza