Before this commit, enum values were serialized as attributes of form
\enum_<width>_<value>
where <value> was a decimal signed integer.
This has multiple drawbacks:
* Enums with large values would be hard to process for downstream
tooling that cannot parse arbitrary precision decimals. (In fact
Yosys also did not correctly process enums with large values,
and would overflow `int`.)
* Enum value attributes were not confined to their own namespace,
making it harder for downstream tooling to enumerate all such
attributes, as opposed to looking up any specific value.
* Enum values could not include x or z, which are explicitly
permitted in the SystemVerilog standard.
After this commit, enum values are serialized as attributes of form
\enum_value_<value>
where <value> is a bit sequence of the appropriate width.
By operating at a layer of abstraction over the rather clumsy Intel primitives,
we can avoid special hacks like `dffinit -highlow` in favour of simple techmapping.
This also makes the primitives much easier to manipulate, and more descriptive
(no more cyclonev_lcell_comb to mean anything from a LUT2 to a LUT6).
In particular inside class declarations, a static const
assignment is technically not a definition, while constexpr is.
Signed-off-by: Henner Zeller <h.zeller@acm.org>
Detect the places in the $alu where the carry bit is constant (due to
const A[i] == B[i] ^ BI) and split it into smaller $alu at these points.
Also, make the existing const-carry detection for low bits more generic
(now handles cases where both BI and CI are constant, but not equal to
one another).
Fixes#1912.
This commit makes it possible to use several cxxrtl-generated files
in one application, as well as compiling cxxrtl-generated code as
a separate compilation unit.
The make targets echo-yosys-ver, echo-git-ver and echo-abc-rev can be
used to programmatically extract contents of make variables for external
scripts. Unfortunately, when a Makefile.conf exists, its contents would
also be echoed, making the output almost unusable. This patch
selectively disables this functionality for these special targets.