ghdl-yosys-plugin compilation failed

Question

I am about to test GHDL and Yosys as a replacement of EDA proprietary design flows, for my students. My point is about VHDL synthesis.

I have a fresh install of several tools : trellis (ECP5), yosys, nexpnr, fujprog (ulx3s).

GHDL is also installed for a longer time but it is supposed to include synthesis also (--synth option works).

ghdl -v 
GHDL 1.0-dev (v0.37.0-208-g2c66a8bd) [Dunoon edition]
Compiled with GNAT Version: Community 2019 (20190517-83)
llvm code generator

It seems that I also need ghdl-yosys-plugin. However, the install does not work for me.

I get a bunch of error messages :

make GHDL=/opt/ghdl/bin/ghdl
yosys-config --exec --cxx -c --cxxflags -o ghdl.o src/ghdl.cc -fPIC -DYOSYS_ENABLE_GHDL -I/opt/ghdl/include -O
src/ghdl.cc:361:2: error: unknown type name 'Attribute'
        Attribute attr = get_first_attribute (inst);
        ^
src/ghdl.cc:361:19: error: use of undeclared identifier 'get_first_attribute'
        Attribute attr = get_first_attribute (inst);
                         ^
src/ghdl.cc:379:7: error: use of undeclared identifier 'Id_Posedge'; did you mean 'Id_Edge'?
        case Id_Posedge:
             ^~~~~~~~~~
             Id_Edge

etc

I am missing something. Can someone help ?

Thanks in advance JCLL

Answer 1

As I suspected (despite versioning that seemed correct), a fresh new install of GHDL fixed the issue.

Answer 2

i did some investigating: ghdl has undergone some restructuring, for proper FHS compliance. for example this commit https://github.com/ghdl/ghdl/commit/66cd5e0aa897b947533d269535fde4c0852472c2 and further commits show some renaming which ensures compliance with FHS conventions. files that used to be installed as /usr/local/include/ghdhsynth.h are now in /usr/local/include/ghdl

however because there are two completely separate pieces of software involved here (ghdl and yosys-ghdl-plugin) you have to (a) keep them in sync and (b) ensure that prior-installed ghdl headers are manually cleared out HOWEVER

manually deleting the installed files in /usr/local/include and reinstalling may not help if you cross over the threshold of commits from stable to developer releases on one but not the other, because older versions of yosys-ghdl-plugin were also not FHS convention-compliant. or, if you don't get them exactly right (i had to check the git log commit timestamps for both ghdl and ghdl-yosys-plugin in order to get a match), you get the general idea

if you really want to use a mis-matched version of ghdl and ghdl-yosys-plugin (YMMV here) then there are a few solutions:

1. manually copy the files in /usr/local/include/ghdl into /usr/local/include. this is a really dreadful hack that will need repeating each time you re-install ghdl.

2. modify the yosys-ghdl-plugin Makefile to include "-I/usr/local/include/ghdl" in CFLAGS or ALL_CFLAGS

3. in ghdl/synth.h and anywhere you see ghdl/synth.h used replace it with just "synth.h", likewise with synth_gates.h.

bear in mind that all of these are absolutely awful, totally not guaranteed to work, and you are way better off making sure that the versions being used are properly in sync.

it also does not help that some things from yosys latest master are also being removed, on which yosys-ghdl-plugin relies, to compile! as of writing i have found that tag yosys-1.13, ghdl-plugin commit c9b05e481423c, and ghdl commit 263c843ed49 will compile and work. however if i update to latest ghdl master (0e46300) microwatt fails to build, so i am sticking with 263c843 for now.

YMMV, hopefully however that gives you some insights rather than considering these complex and fantastically useful pieces of interlinked software to be opaque black boxes.