E-conversion
Translation from simplified Verilog modules into E modules.
The conversion from Verilog to E is mostly straightforward because
here we only try to support an extremely limited subset of Verilog. The basic
idea is that other transforms should first be used to simplify more
complex, "original" input modules into this simple subset.
Here are some basic expectations:
- Each module we need to process will include net declarations and submodule
instances, but will not have any assignments, gates, always blocks, parameters,
registers, variables, etc. These other constructs should be simplified away
before E conversion.
- Each module instance will have well-formed port connections that contain
only sliceable expressions. This lets
us deal with everything purely at the bit level.
We have checks to ensure our assumptions hold, and these checks will result
in fatal warnings if the modules contain unsupported constructs. See in
particular vl-module-check-e-ok and vl-module-check-port-bits.
We process the modules in dependency order, and aside from sanity checking
there are basically two steps for each module we need to convert:
- We produce a preliminary E module by exploding the module's vectors into individual bits,
and converting the module instances into E occurrences for the submodules.
- This preliminary E module is almost a proper E module, but it might have
some wires that are driven by multiple occurrences. As a second step, we
rewrite the preliminary module to resolve these multiply driven wires. This
ensures that every wire has exactly one driver.
Some final sanity checking is done to ensure that the module's inputs and
outputs are properly marked and there is no "backflow" occurring.
The resulting E module for each Verilog module is saved in the esim
field of each vl-module-p.
Subtopics
- Vl-ealist-p
- Alist binding module names to E modules.
- Modinsts-to-eoccs
- How we convert Verilog modules instances into (preliminary) E module
occurrences.
- Vl-module-make-esim
- Convert a Verilog module into an E module.
- Exploding-vectors
- How we convert Verilog wires (which might be vectors) into E
wires (which are just bits).
- Resolving-multiple-drivers
- How we replace multiply driven wires with explicit resolution
modules.
- Vl-modulelist-make-esims
- Extend vl-module-make-esim across a list of modules.
- Vl-module-check-e-ok
- Check for unsupported constructs.
- Vl-collect-design-wires
- Collect all symbols for design-visible wires and return them as a
flat list of bits.
- Adding-z-drivers
- How we ensure every wire is driven.
- Vl-design-to-e
- Top-level function for E conversion.
- Vl-design-to-e-check-ports
- Make sure that the module port/port-declarations agree and that there
are no unsupported constructs.
- Vl-design-to-e-main
- Port-bit-checking
- A well-formedness check to ensure that ports and port declarations
agree, and are simple enough for E conversion.
