This fixes some dfflegalize equivalence checks, and breaks others — and
I strongly suspect the others are due to bad support for multiple
async inputs in `proc` (in particular, lack of proper support for
dlatchsr and sketchy circuits on dffsr control inputs).
Those can be created by `opt_dff` when optimizing `$adff` with const
clock, or with D == Q. Make dfflegalize do the opposite transform
when such dlatches would be otherwise unimplementable.
This ensures that, when both sync and async FFs are available and abc9
is involved, the sync FFs will be used, and will thus remain available
for sequential synthesis.
I think these were probably missed by accident. Spotted because GCC
spits out lots of messages like this:
passes/techmap/dfflegalize.cc:114:7: warning: zero-length gnu_printf format string [-Wformat-zero-length]
114 | log("");
| ^~
(because we tell GCC that the first argument to log() looks like a
printf control string in log.h, and a zero length such string triggers
a warning).
Look for unique connections in the containing module with the $anyconst port Y SigBit on the RHS and use those. If no such connection is found, fall back to using the name of the $anyconst port Y SigBit.
The new types include:
- FFs with async reset and enable (`$adffe`, `$_DFFE_[NP][NP][01][NP]_`)
- FFs with sync reset (`$sdff`, `$_SDFF_[NP][NP][01]_`)
- FFs with sync reset and enable, reset priority (`$sdffs`, `$_SDFFE_[NP][NP][01][NP]_`)
- FFs with sync reset and enable, enable priority (`$sdffce`, `$_SDFFCE_[NP][NP][01][NP]_`)
- FFs with async reset, set, and enable (`$dffsre`, `$_DFFSRE_[NP][NP][NP][NP]_`)
- latches with reset or set (`$adlatch`, `$_DLATCH_[NP][NP][01]_`)
The new FF types are not actually used anywhere yet (this is left
for future commits).
1. Infinite loop in the optimization procedure when the first solution found while maximizing is at zero.
2. A signed-ness issue when maximizing.
3. Erroneously entering bisection mode with no wire to optimize.
Before this commit, `flatten` matched the template objects with
the newly created objects solely by their name. Because of this,
it could be confused by code such as:
module bar();
$dff a();
endmodule
module foo();
bar b();
$dff \b.a ();
endmodule
After this commit, `flatten` avoids every possible case of name
collision.
Fixes#2106.
log_signal can result in a string with spaces (when bit selection is
involved), which breaks the rule of IdString not containing whitespace.
Instead, remove the sigspec from the name entirely — given that the
resulting wire will have no users, it will be removed later anyway,
so its name doesn't really matter.
Fixes#2118
`flatten` cannot derive modules in most cases because that would just
yield processes, and it does not support `-autoproc`; in practice
`flatten` has to be preceded by a call to `hierarchy`, which makes
deriving unnecessary.
After splitting the passes, some options can never be activated,
and most conditions involving them become dead. Remove them, and also
all of the newly dead code.
Although the two passes started out very similar, they diverged over
time and now have little in common. Moreover, `techmap` is extremely
complex while `flatten` does not have to be, and this complexity
interferes with improving `flatten`.
The $div and $mod cells use truncating division semantics (rounding
towards 0), as defined by e.g. Verilog. Another rounding mode, flooring
(rounding towards negative infinity), can be used in e.g. VHDL. The
new $divfloor cell provides this flooring division.
This commit also fixes the handling of $div in opt_expr, which was
previously optimized as if it was $divfloor.
The $div and $mod cells use truncating division semantics (rounding
towards 0), as defined by e.g. Verilog. Another rounding mode, flooring
(rounding towards negative infinity), can be used in e.g. VHDL. The
new $modfloor cell provides this flooring modulo (also known as "remainder"
in several languages, but this name is ambiguous).
This commit also fixes the handling of $mod in opt_expr, which was
previously optimized as if it was $modfloor.
Before this patch, the code passed around std::string objects by
value. It's probably not a hot-spot, but it can't hurt to avoid the
copying.
Removing the copy and clean-up code means the resulting code is ~6.1kb
smaller when compiled with GCC 9.3 and standard settings.
- Pass a string argument by reference
- Avoid multiple calls to IdString::str and IdString::c_str
- Avoid combining checks for size > 0 and first char (C strings are
null terminated, so foo[0] != '\0' implies that foo has positive
length)
With GCC 9.3, at least, compiling select.cc spits out a warning about
an implausible bound being passed to strncmp. This comes from inlining
IdString::compare(): it turns out that passing std::string::npos as a
bound to strncmp triggers it.
This patch replaces the compare call with a memcmp with the same
effect. The repeated calls to IdString::c_str are slightly
inefficient, but I'll address that in a follow-up commit.
This code originally comes from commit 458a940. When an interface is
used via a modport, code in genrtlil.cc sets '\\interface_type' and
'\\interface_modport' properties on the wire.
In hierarchy.cc, we pick up the modport name and add it to a dict
called modports_used_in_submodule (that maps connection source to
modport name).
Before this patch, the modport name is retrieved as a strpool and then
iterated over in an arbitrary order, discarding all entries but the
last. In practice, the pool will always have 0 or 1 entries because
the string used to construct it is a valid identifier, so doesn't
contain any pipe symbols.
This patch changes the code to retrieve the modport name as just a
string. This will have the same effect in practice, but may be a bit
less confusing!
The code also gets moved down closer to where the result is used,
which might be a bit more efficient since we won't always get as far
as the check.
The patch also removes some commented-out code, which I think was
intended to add some typechecking at some point, but was never
implemented. Since this dates back to October 2018, I think it makes
more sense to just take it out.
Ensures that "BV" is the logic whenever solving an exists-forall problem with Yices, moves the "(set-logic ...)" directive above any non-info line, sets the `ef-max-iters` parameter to a very high number when using Yices in exists-forall mode so as not to prematurely abandon difficult problems, and does not provide the incompatible "--incremental" Yices argument when in exists-forall mode.
Marcelina Kościelnicka
Eddie Hung
Rupert Swarbrick
clairexen
Alberto Gonzalez
whitequark
Miodrag Milanović
Xiretza
N. Engelhardt
Anonymous Maarten