Commit Graph

205 Commits

Author SHA1 Message Date
whitequark 2db4137514
Merge pull request #2874 from whitequark/cxxrtl-fix-2589
cxxrtl: run hierarchy pass regardless of (*top*) attribute presence
2021-07-16 11:12:19 +00:00
whitequark efc43270fa
Merge pull request #2873 from whitequark/cxxrtl-fix-2500
cxxrtl: emit debug items for unused public wires
2021-07-16 11:01:10 +00:00
whitequark 5b003d6e5c cxxrtl: run hierarchy pass regardless of (*top*) attribute presence.
The hierarchy pass does a lot more than just finding the top module,
mainly resolving implicit (positional, wildcard) module connections.

Fixes #2589.
2021-07-16 10:27:47 +00:00
whitequark 09218896d6 cxxrtl: emit debug items for unused public wires.
This greatly improves debug information coverage.

Fixes #2500.
2021-07-16 10:14:40 +00:00
whitequark b28ca7f5ac cxxrtl: don't expect user cell inputs to be wires.
Ports can be connected to constants, too. (Usually resets.)

Fixes #2521.
2021-07-16 09:51:52 +00:00
whitequark 44a3d924ce cxxrtl: don't mark buffered internal wires as UNUSED for debug.
Public wires may alias buffered internal wires, so keep BUFFERED
wires in debug information even if they are private. Debug items are
only created for public wires, so this does not otherwise affect how
debug information is emitted.

Fixes #2540.
Fixes #2841.
2021-07-16 07:54:49 +00:00
whitequark 54b6cb645f cxxrtl: mark dead local wires as unused even with inlining disabled.
Fixes #2739.
2021-07-15 22:27:27 +00:00
Marcelina Kościelnicka 8bf9cb407d kernel/mem: Add a coalesce_inits helper.
While this helper is already useful to squash sequential initializations
into one in cxxrtl, its main purpose is to squash overlapping masked memory
initializations (when they land) and avoid having to deal with them in
cxxrtl runtime.
2021-07-13 15:59:11 +02:00
Marcelina Kościelnicka 37506d737c cxxrtl: Support memory writes in processes. 2021-07-12 18:27:48 +02:00
Marcelina Kościelnicka af7fa62251 cxxrtl: Add support for memory read port reset. 2021-07-12 18:27:48 +02:00
Marcelina Kościelnicka be5cf29699 cxxrtl: Add support for mem read port initial data. 2021-07-12 18:27:48 +02:00
Marcelina Kościelnicka d5c9595668 cxxrtl: Convert to Mem helpers.
This *only* does conversion, but doesn't add any new functionality —
support for memory read port init/reset is still upcoming.
2021-07-12 18:27:48 +02:00
whitequark ab76d9cec5 cxxrtl: don't assert on edge sync rules tied to a constant.
These are commonly the result of tying an async reset to an inactive
level.
2021-03-07 14:29:30 +00:00
whitequark d1de08e38a cxxrtl: allow `always` sync rules in debug_eval.
These can be produced from `always @*` processes, if `-noproc`
is used.
2021-03-07 14:28:45 +00:00
whitequark 9dd813374e
Merge pull request #2635 from whitequark/cxxrtl-memrd-async-addr
cxxrtl: follow aliases to outlines when emitting $memrd.ADDR
2021-03-05 05:30:19 -08:00
whitequark 06da2e0f18
Merge pull request #2634 from whitequark/cxxrtl-debug-wire-types
cxxrtl: add pass debug flag to show assigned wire types
2021-03-05 04:57:22 -08:00
whitequark 14ce8bdaa6 cxxrtl: follow aliases to outlines when emitting $memrd.ADDR. 2021-03-05 12:09:02 +00:00
whitequark 8471808834 cxxrtl: add pass debug flag to show assigned wire types.
Refs #2543.
2021-03-05 11:58:59 +00:00
whitequark a9a873a1d2 cxxrtl: don't crash on empty designs. 2021-03-05 11:05:19 +00:00
whitequark a77fa6709b
Merge pull request #2563 from whitequark/cxxrtl-msvc
cxxrtl: do not use `->template` for non-dependent names
2021-01-26 21:55:12 +00:00
whitequark 4b6e764c46 cxxrtl: do not use `->template` for non-dependent names.
This breaks build on MSVC but not GCC/Clang.
2021-01-26 18:09:53 +00:00
Iris Johnson c8415884d1 Improves the previous commit with a more complete coverage of the cases 2021-01-15 13:59:20 -06:00
Iris Johnson 86607d0fdc Handle sliced bits as clock inputs (fixes #2542) 2021-01-14 16:36:21 -06:00
whitequark f14074d2c2 cxxrtl: don't crash generating debug information for unused wires. 2020-12-22 06:51:38 +00:00
whitequark 7378194169 cxxrtl: split processes into sync and case nodes.
Similar to the treatment of black boxes, splitting processes into two
scheduling nodes adds sufficient freedom so that netlists with
well-behaved processes (e.g. those emitted by nMigen) can immediately
converge.

Because processes are not emitted into edge-triggered regions, this
approach has comparable performance to -O5 (without -noproc), which
is substantially slower than -O6.
2020-12-22 03:48:09 +00:00
whitequark b2221c1077 cxxrtl: completely rewrite netlist layout code.
The exact shape of C++ code emitted by CXXRTL has a critical effect
on performance, both compile-time and runtime. CXXRTL's performance
greatly improved when it started localizing and inlining wires, not
only because this assists the optimizer and register allocator, but
also because inlining code into edge-triggered regions cuts the time
spent in eval() by at least a factor of two.

However, the logic of netlist layout has always been ad-hoc, fragile,
and very hard to understand and modify. After commit ece25a45, which
introduced outlining, the same logic started being applied to two
distinct netlists at once instead of one, which barely worked.

This commit does four major changes:
  * There is now a single unambiguous source of truth (per subgraph)
    for the layout of any emitted wire.
  * Netlist layout is now done entirely during analysis using well
    known graph algorithms; no graph operations happen when emitting.
  * Netlist layout now happens completely separately for eval() and
    debug_eval() subgraphs.
  * Unreachable (within subgraph scope) netlist nodes are now neither
    emitted nor considered for wire inlining decisions.
The netlist layout code should also now closely match the described
semantics.

As a part of this large cleanup, it includes many miscellaneous
improvements:
  * The "bare minimum" debug level introduced in commit dd6a761d was
    split into two levels; -g1 now emits debug information *only* for
    inputs and state wires, and -g2 now emits debug information for
    all public members. The old behavior matches -g2. This is done
    to avoid bloat on low optimization levels.
  * Debug aliases and inlined connections are now handled separately,
    and complex RHS never interferes with inlined connections.
  * Aliases to outlined wires now carry a pointer to the outline.
  * Cell sync outputs can now be emitted in debug_eval().
  * Black box debug information now includes comb/sync driver flags.
  * The comment emitted for inlined cells is now accurate.
  * Debug information statistics now has less noise.
  * Netlist layout code is now much better documented.

Due to more precise inlining decisions, unmodified (i.e. with no
Yosys script being used) netlists now have much more logic inlined
into edge-triggered regions. On Minerva SoC SRAM, this improves
runtime by 20-25% across compilers and optimization levels.

Due to more precise reachability analysis, much less C++ code is now
emitted, especially at the maximum debug level. On Minerva SoC SRAM,
this improves clang compile time by 30-50% depending on options.
gcc is not affected.
2020-12-22 03:48:09 +00:00
whitequark e825cf9d73 cxxrtl: simplify logic choosing wire type. NFCI. 2020-12-21 07:24:52 +00:00
whitequark 6f42b26cea cxxrtl: clarify node use-def construction. NFCI. 2020-12-21 07:24:52 +00:00
whitequark 406f866659 cxxrtl: fix typo. 2020-12-21 07:24:52 +00:00
whitequark b9721bedf0 cxxrtl: speed up bit repeats (sign extends, etc).
On Minerva SoC SRAM, depending on the compiler, this change improves
overall time by 4-7%.
2020-12-21 02:20:34 +00:00
whitequark 40ca9d038b cxxrtl: speed up commits on clang.
On Minerva SoC SRAM compiled with clang-11, this change cuts commit
time in half (!) and overall time by 20%. When compiled with gcc-10,
there is no difference.
2020-12-21 02:20:30 +00:00
whitequark 3d3ea5099d cxxrtl: use `static inline` instead of `inline` in the C API.
In C, non-static inline functions require an implementation elsewhere
(even though the body is right there in the header). It is basically
never desirable to use those as opposed to static inline ones.
2020-12-20 14:48:16 +00:00
whitequark d889a3df35 cxxrtl: print names of cells inlined in connections. 2020-12-15 11:02:38 +00:00
whitequark f75bc6c7aa cxxrtl: disable optimization of debug_items().
Implementing outlining has greatly increased the amount of debug
information in a typical build, and consequently exposed performance
issues in C++ compilers, which are similar for both GCC and Clang;
the compile time of Minerva SoC SRAM increased almost twofold.

Although one would expect the slowdown to be caused by the increased
use of templates in `debug_eval()`, it is actually almost entirely
attributable to optimizations and codegen for `debug_items()`.

Fortunately, it is neither possible nor desirable to optimize
`debug_items()`: in most cases it is called exactly once, and its
body is a linear sequence of calls with unique arguments.

This commit turns off optimizations for `debug_items()` on GCC and
Clang, improving -Os compile time of Minerva SoC SRAM by ~40% (!)
2020-12-15 11:02:38 +00:00
whitequark 4d40595d64 cxxrtl: make alias analysis outlining-aware.
Before this commit, if a sequence of wires assigned in a chain would
terminate on a cell, none of the wires would get marked as aliases,
and typically all of the public wires would get outlined. The reason
for this behavior is that alias analysis predates outlining and in
fact runs before it.

After this commit, alias analysis runs after outlining and considers
outlined wires valid aliasees. More importantly, if the chained wires
contain any valid aliasees, then all of the wires are aliased to
the one that is topologically deepest.

Aliased wires incur virtually no overhead for the VCD writer, unlike
outlined wires that would otherwise take their place. On Minerva SoC
SRAM, size of the full VCD dump is reduced by ~65%, and throughput
is increased by ~55%.
2020-12-15 11:02:38 +00:00
whitequark dd6a761db0 cxxrtl: add a "bare minimum" debug information level.
Useful to reduce overhead when no debug capabilities are necessary
except for access to design state.
2020-12-14 01:27:56 +00:00
whitequark ece25a45d4 cxxrtl: implement debug information outlining.
Aggressive wire localization and inlining is necessary for CXXRTL to
achieve high performance. However, that comes with a cost: reduced
debug information coverage. Previously, as a workaround, the `-Og`
option could have been used to guarantee complete coverage, at a cost
of a significant performance penalty.

This commit introduces debug information outlining. The main eval()
function is compiled with the user-specified optimization settings.
In tandem, an auxiliary debug_eval() function, compiled from the same
netlist, can be used to reconstruct the values of localized/inlined
signals on demand. To the extent that it is possible, debug_eval()
reuses the results of computations performed by eval(), only filling
in the missing values.

Benchmarking a representative design (Minerva SoC SRAM) shows that:
  * Switching from `-O4`/`-Og` to `-O6` reduces runtime by ~40%.
  * Switching from `-g1` to `-g2`, both used with `-O6`, increases
    compile time by ~25%.
  * Although `-g2` increases the resident size of generated modules,
    this has no effect on runtime.

Because the impact of `-g2` is minimal and the benefits of having
unconditional 100% debug information coverage (and the performance
improvement as well) are major, this commit removes `-Og` and changes
the defaults to `-O6 -g2`.

We'll have our cake and eat it too!
2020-12-14 01:27:27 +00:00
whitequark 3b5a1314cd cxxrtl: rename "elision" to "inlining". NFC.
"Elision" in this context is an unusual and not very descriptive term
whereas "inlining" is common and straightforward. Also, introducing
"inlining" makes it easier to introduce its dual under the obvious
name "outlining".
2020-12-13 15:34:00 +00:00
whitequark 57759c3d1f cxxrtl: fix outdated comment. NFC. 2020-12-13 15:33:58 +00:00
whitequark ac1a78923a cxxrtl: use IdString::isPublic(). NFC. 2020-12-13 15:33:55 +00:00
whitequark e4aa8bc96b cxxrtl: don't overwrite buffered inputs.
Before this commit, a cell's input was always assigned like:

    p_cell.p_input = (value...);

If `p_input` is buffered (e.g. if the design is built at -O0), this
is not correct. (In practice, this breaks clocking.) Unfortunately,
the incorrect design was compiled without diagnostics because wire<>
was move-assignable and also implicitly constructible from value<>.

After this commit, cell inputs are no longer incorrectly assumed to
always be unbuffered, and wires are not assignable from values.
2020-12-11 23:32:06 +00:00
whitequark e89f6ae819 cxxrtl: allow customizing the root module path in the C API. 2020-12-03 01:58:02 +00:00
whitequark 3e13cfe53d
Merge pull request #2468 from whitequark/cxxrtl-assert
cxxrtl: use CXXRTL_ASSERT for RTL contract violations instead of assert
2020-12-02 23:36:22 +00:00
whitequark 3cb109f54b
Merge pull request #2469 from whitequark/cxxrtl-no-clk
cxxrtl: fix crashes caused by a floating or constant clock input
2020-12-02 23:36:03 +00:00
whitequark 7067f0d788 cxxrtl: fix crashes caused by a floating or constant clock input.
E.g. in:

    module test;
        wire clk = 0;
        reg data;
        always @(posedge clk)
            data <= 0;
    endmodule
2020-12-02 21:43:25 +00:00
whitequark aa0a15a42c cxxrtl: use CXXRTL_ASSERT for RTL contract violations instead of assert.
RTL contract violations and C++ contract violations are different:
the former depend on the netlist and will never violate memory safety
whereas the latter may. When loading a CXXRTL simulation into another
process, RTL contract violations should generally not crash it, while
C++ contract violations should.
2020-12-02 19:41:00 +00:00
whitequark 5beab5bc17 cxxrtl: provide a way to perform unobtrusive power-on reset.
Although it is always possible to destroy and recreate the design to
simulate a power-on reset, this has two drawbacks:
  * Black boxes are also destroyed and recreated, which causes them
    to reacquire their resources, which might be costly and/or erase
    important state.
  * Pointers into the design are invalidated and have to be acquired
    again, which is costly and might be very inconvenient if they are
    captured elsewhere (especially through the C API).
2020-12-02 08:25:27 +00:00
whitequark 65083e9520 cxxrtl: run `hierarchy -auto-top` if no top module is present.
In most cases, a CXXRTL simulation would use a top module, either
because this module serves as an entry point to the CXXRTL C API,
or because the outputs of a top module are unbuffered, improving
performance. Taking this into account, the CXXRTL backend now runs
`hierarchy -auto-top` if there is no top module. For the few cases
where this behavior is unwanted, it now accepts a `-nohierarchy`
option.

Fixes #2373.
2020-11-02 19:18:56 +00:00
whitequark 2ba05f5c31 cxxrtl: don't assert on non-constant $meminit inputs.
Fixes #2129.
2020-11-01 15:57:20 +00:00
whitequark cdf4ce9871 cxxrtl: don't assert on wires with multiple drivers.
Fixes #2374.
2020-11-01 12:49:30 +00:00
whitequark 691418e13a cxxrtl: expose driver kind in debug information.
This can be useful to determine whether the wire should be a part of
a design checkpoint, whether it can be used to override design state,
and whether driving it may cause a conflict.
2020-09-02 18:00:12 +00:00
whitequark c7b2f07edf cxxrtl: improve handling of FFs with async inputs (other than CLK).
Before this commit, the meaning of "sync def" included some flip-flop
cells but not others. There was no actual reason for this; it was
just poorly defined.

After this commit, a "sync def" means that a wire holds design state
because it is connected directly to a flip-flop output, and may never
be unbuffered. This is not affected by presence of async inputs.
2020-09-02 18:00:12 +00:00
whitequark b025ee0aa6 cxxrtl: expose port direction in debug information.
This can be useful to distinguish e.g. a combinatorially driven wire
with type `CXXRTL_VALUE` from a module input with the same type, as
well as general introspection.
2020-09-02 17:19:11 +00:00
whitequark 8d6e5c6391 cxxrtl: fix typo in comment. NFC. 2020-09-02 15:23:49 +00:00
whitequark d880f6eda2 cxxrtl: fix inaccuracy in CXXRTL_ALIAS documentation. NFC.
Nodes driven by a constant value have type CXXRTL_VALUE and their
`next` pointer set to NULL. (This is already documented.)
2020-09-02 15:23:47 +00:00
Andy Knowles 5829d16fcd
cxxrtl.h: Fix incorrect CarryOut in alu() 2020-08-12 21:04:34 +02:00
Andy Knowles 1227c3681b cxxrtl.h: Fix incorrect CarryOut in alu when Bits % 32 != 0 && Invert == False 2020-08-12 11:32:57 +02:00
whitequark a5cf000377 cxxrtl: fix typo. NFC. 2020-07-14 16:10:30 +00:00
whitequark 5349a922e4 cxxrtl: expose eval() and commit() via the C API. 2020-07-12 23:34:18 +00:00
whitequark ab59e33b2b cxxrtl: add missing extern "C".
This bug was hidden if a header was generated.
2020-07-09 17:52:52 +00:00
whitequark a746c4b605 cxxrtl: update help text. 2020-06-26 08:30:44 +00:00
Marcelina Kościelnicka cb9a8ad0f2 cxxrtl: Add support for the new FF types. 2020-06-24 02:15:08 +02:00
whitequark ede4b10da8
Merge pull request #2173 from whitequark/use-cxx11-final-override
Use C++11 final/override/[[noreturn]]
2020-06-19 06:15:33 +00:00
whitequark 962a2f3bff cxxrtl: add .get() and .set() accessors on value<> and wire<>.
For several reasons:
  * They're more convenient than accessing .data.
  * They accommodate variably-sized types like size_t transparently.
  * They statically ensure that no out of range conversions happen.

For now these are only provided for unsigned integers, but eventually
they should be provided for signed integers too. (Annoyingly this
affects conversions to/from `char` at the moment.)

Fixes #2127.
2020-06-19 02:31:35 +00:00
whitequark 7191dd16f9 Use C++11 final/override keywords. 2020-06-18 23:34:52 +00:00
whitequark 8344846787
Merge pull request #2167 from whitequark/cxxrtl-fix-ndebug
cxxrtl: don't compute vital values in log_assert()
2020-06-18 16:57:51 +00:00
whitequark 3c4e974d7b cxxrtl: don't compute vital values in log_assert().
This breaks NDEBUG builds.

Fixes #2166.
2020-06-17 19:27:47 +00:00
whitequark c4f20f744b
Merge pull request #2163 from jfng/cxxrtl-blackbox-debuginfo
cxxrtl: restrict the debug info of a blackbox to its ports.
2020-06-17 06:07:41 +00:00
whitequark eaf66037a5
Merge pull request #2160 from whitequark/cxxrtl-fix-warning
cxxrtl: avoid unused variable warning for transparent $memrd ports
2020-06-17 06:06:58 +00:00
Jean-François Nguyen 8d98c3861d cxxrtl: restrict the debug info of a blackbox to its ports. 2020-06-16 15:30:56 +02:00
whitequark 334ec5fa0a
Merge pull request #2159 from MerryMage/cxxrtl-mul
cxxrtl: Implement chunk-wise multiplication
2020-06-15 06:08:17 +00:00
whitequark 8d70f7abf9 cxxrtl: avoid unused variable warning for transparent $memrd ports. NFC. 2020-06-15 06:00:16 +00:00
MerryMage f7ae9b0851 cxxrtl: Implement chunk-wise multiplication 2020-06-15 05:54:57 +01:00
whitequark 9d0f1aa222
Merge pull request #2158 from miek/sshr-sign-extension
cxxrtl: fix sshr sign-extension.
2020-06-15 01:37:05 +00:00
Mike Walters 66a2de2912 cxxrtl: fix sshr sign-extension. 2020-06-15 01:01:49 +01:00
whitequark 971a765155
Merge pull request #2151 from whitequark/cxxrtl-fix-rzext
cxxrtl: fix rzext()
2020-06-13 22:18:35 +00:00
whitequark dc6961f3d4
Merge pull request #2145 from whitequark/cxxrtl-splitnets
cxxrtl: handle multipart signals
2020-06-13 04:23:22 +00:00
whitequark 107911dbec cxxrtl: always inline internal cells and slice/concat operations.
This can result in massive reduction in runtime, up to 50% depending
on workload. Currently people are using `-mllvm -inline-threshold=`
as a workaround (with clang++), but this solution is more portable.
2020-06-13 01:52:06 +00:00
whitequark 6cf02ed94f cxxrtl: fix rzext().
This was a correctness issue, but one of the consequences is that it
resulted in jumps in generated machine code where there should have
been none. As a side effect of fixing the bug, Minerva SoC became 10%
faster.
2020-06-13 00:49:44 +00:00
whitequark b793e4753b cxxrtl: elide $pmux cells.
On Minerva, this improves runtime by around 10%, mostly by ensuring
that the logic driving FFs is packed into edge conditionals.
2020-06-12 02:40:30 +00:00
whitequark d5ecd4a570 cxxrtl: annotate port direction as comments. 2020-06-12 00:35:18 +00:00
whitequark 29bd81d662 cxxrtl: unbuffer output wires of toplevel module.
Without unbuffering output wires of, at least, toplevel modules, it
is not possible to have most designs that rely on IO via toplevel
ports (as opposed to using exclusively blackboxes) converge within
one delta cycle. That seriously impairs the performance of CXXRTL.

This commit avoids unbuffering outputs of all modules solely so that
in future, CXXRTL could gain fully separate compilation, and not for
any present technical reason.
2020-06-12 00:31:57 +00:00
whitequark cd7bf115b6 cxxrtl: simplify unbuffering of input wires.
This also fixes an edge case with (*keep*) input ports.
2020-06-12 00:31:57 +00:00
whitequark 8d712b1095 cxxrtl: handle multipart signals.
This avoids losing design visibility when using the `splitnets` pass.
2020-06-11 19:34:35 +00:00
whitequark fa04b19670 cxxrtl: expose RTLIL::{Wire,Memory}->start_offset in debug info. 2020-06-11 12:43:17 +00:00
whitequark 8a4841d786
Merge pull request #2141 from whitequark/cxxrtl-cxx11
cxxrtl: various compiler compatibility fixes
2020-06-10 17:10:15 +00:00
whitequark 6021ff727d cxxrtl: restore C++11 compatibility.
This is necessary to be able to build CXXRTL models via yosys-config.
2020-06-10 15:57:07 +00:00
whitequark cde99e696a cxxrtl: fix a few gcc warnings. 2020-06-10 15:57:07 +00:00
whitequark 574f5cb5b2 Fix formatting. NFC. 2020-06-10 15:48:40 +00:00
whitequark 0955a603c8 cxxrtl: disambiguate values/wires and their aliases in debug info.
With this change, it is easier to see which signals carry state (only
wire<>s appear as `reg` in VCD files) and to construct a minimal
checkpoint (CXXRTL_WIRE debug items represent the canonical smallest
set of state required to fully reconstruct the simulation).
2020-06-10 14:39:45 +00:00
whitequark 5467fe563a cxxrtl: allow unbuffering without localizing.
Although logically two separate steps, these were treated as one for
historic reasons. Splitting the two makes it possible to have designs
that are only 2× slower than fastest possible (and are without extra
delta cycles) that allow probing all public wires.
2020-06-09 21:50:09 +00:00
whitequark 970ec34e70 cxxrtl: order -On levels as localize, elide instead of the reverse.
Historically, elision was implemented before localization, so levels
with elision are lower than corresponding levels with localization.
This is unfortunate for two reasons:
  1. Elision is a logical subset of localization, since it equals to
     not giving a name to a temporary.
  2. "Localize" currently actually means "unbuffer and localize",
     and it would be useful to split those steps (at least for
     public wires) for improved design visibility.
2020-06-09 20:55:40 +00:00
whitequark ba11060e59 cxxrtl: factor out -noproc/-noflatten from -O.
Although these options can be thought of as optimizations, they are
essentially orthogonal to the core of -O, which is managing signal
buffering and scope. Going from -O4 to -O2 means going from limited
to complete design visibility, yet in both cases proc and flatten
are desirable.
2020-06-09 20:18:07 +00:00
whitequark bbfe55a8d0 cxxrtl: fix two buggy split_by functions. 2020-06-09 11:05:35 +00:00
whitequark 74e3ac2449
Merge pull request #2126 from whitequark/cxxrtl-non-ext-logic-ops
cxxrtl: ignore cell input signedness when it is irrelevant
2020-06-09 09:54:09 +00:00
whitequark ef4e159447 cxxrtl: ignore cell input signedness when it is irrelevant.
Before this commit, Verilog expressions like `x && 1` would result in
references to `logic_and_us` in generated CXXRTL code, which would
not compile. After this commit, since cells like that actually behave
the same regardless of signedness attributes, the signedness is
ignored, which also reduces the template instantiation pressure.
2020-06-09 07:26:13 +00:00
whitequark 4e7d837747 cxxrtl: add missing namespace.
Fixes #2124.
2020-06-09 06:26:43 +00:00
whitequark 53688a24b5 cxxrtl: fix format of hdlnames.
The CXXRTL code that handled the `hdlname` attribute implemented
outdated semantics.
2020-06-08 20:19:41 +00:00
whitequark 467152d79f cxxrtl: don't check immutable values for changes in VCD writer.
This commit changes the VCD writer such that for all signals that
have `debug_item.type == VALUE && debug_item.next == nullptr`, it
would only sample the value once.

Commit f2d7a187 added more debug information by including constant
wires, and decreased the performance of VCD writer proportionally
because the constant wires were still repeatedly sampled; this commit
eliminates the performance hit.
2020-06-08 17:38:11 +00:00
whitequark f2d7a18756 cxxrtl: emit debug information for constant wires.
Constant wires can represent a significant chunk of the design in
generic designs or after optimization. Emitting them in VCD files
significantly improves usability because gtkwave removes all traces
that are not present in the VCD file after reload, and iterative
development suffers if switching a varying signal to a constant
disrupts the workflow.
2020-06-08 17:29:08 +00:00