Doing ABC runs in parallel can actually make things slower when every ABC run requires
spawning an ABC subprocess --- especially when using popen(), which on glibc does not
use vfork(). What seems to happen is that constant fork()ing keeps making the main
process data pages copy-on-write, so the main process code that is setting up each ABC
call takes a lot of minor page-faults, slowing it down.
The solution is pretty straightforward although a little tricky to implement.
We just reuse ABC subprocesses. Instead of passing the ABC script name on the command
line, we spawn an ABC REPL and pipe a command into it to source the script. When that's
done we echo an `ABC_DONE` token instead of exiting. Yosys then puts the ABC process
onto a stack which we can pull from the next time we do an ABC run.
For one of our large designs, this is an additional 5x speedup of the primary AbcPass.
It does 5155 ABC runs, all very small; runtime of the AbcPass goes from 760s to 149s
(not very scientific benchmarking but the effect size is large).
Large circuits can run hundreds or thousands of ABCs in a single AbcPass.
For some circuits, some of those ABC runs can run for hundreds of seconds.
Running ABCs in parallel with each other and in parallel with main-thread
processing (reading and writing BLIF files, copying ABC BLIF output into
the design) can give large speedups.
Currently `assign_map` is rebuilt from the module from scratch every time we invoke ABC.
That doesn't scale when we do thousands of ABC runs over large modules. Instead,
create it once and then maintain incrementally it as we update the module.
ABC's read_lib command has a dont_use
cell list that is configurable by the user.
This PR exposes that option to Yosys.
See
5405d4787a/src/map/scl/scl.c (L285)
for documentation on this option.
Signed-off-by: Ethan Mahintorabi <ethanmoon@google.com>
C does not guarantee that stdout/stderr can be reassigned.
Most platforms do make them assignable, however musl and WASI that
is based on musl do not. WASI does not have `dup2()`; instead it has
its own non-portable version of it that can only assign to previously
allocated fds.
Update the stream redirection code so that it does the right thing
on WASI and other platforms.
This is mostly important for YoWASP builds, since those do not have
a way to build with external ABC (I prototyped it but for some reason
ABC always segfaults when built as an independent Wasm binary...)
After speaking with the author of ABC he let me know that ifraig is a very old command, and that &get; &fraig -x; &put is over 100x faster than ifraig with improved PPA results.
After making the change I confirmed that this is in fact a major speed up. On our internal designs in O(millions) of standard cells we saw multi hour reductions in runtime.
Also included is an improvement to the dress command. Using AIG based transformations removes the spec it SATs against. Proving the input blif will make sure that no matter what commands are run the dress command can still do its job. I noticed a regression against some LUT mapping jobs that prompted me to fix this.
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.
POSIX defines $TMPDIR as containing the pathname of the directory where
programs can create temporary files. On most systems, this variable points to
"/tmp". However, on some systems it can point to a different location.
Without respecting this variable, yosys fails to run on such systems.
Signed-off-by: Mohamed A. Bamakhrama <mohamed@alumni.tum.de>
This includes the following significant changes:
* Patching ezsat and minisat to disable resource limiting code
on WASM/WASI, since the POSIX functions they use are unavailable.
* Adding a new definition, YOSYS_DISABLE_SPAWN, present if platform
does not support spawning subprocesses (i.e. Emscripten or WASI).
This definition hides the definition of `run_command()`.
* Adding a new Makefile flag, DISABLE_SPAWN, present in the same
condition. This flag disables all passes that require spawning
subprocesses for their function.
