This involves very few changes, all typical to WASM ports:
* WASM doesn't currently support threads or atomics so those are
disabled.
* WASM doesn't currently support exceptions so the exception
machinery is stubbed out.
* WASM doesn't (and can't) have mmap(), so an emulation library is
used. That library currently doesn't support MAP_SHARED flags,
so MAP_PRIVATE is used instead.
There is also an update to bring ECP5 bbasm CMake rules to parity
with iCE40 ones, since although it is possible to embed chipdb into
nextpnr on WASM, a 200 MB WASM file has very few practical uses.
The README is not updated and there is no included toolchain file
because at the moment it's not possible to build nextpnr with
upstream boost and wasi-libc. Boost requires a patch (merged, will
be available in boost 1.74.0), wasi-libc requires a few unmerged
patches.
A CMake option 'BUILD_HEAP' (default on) configures building of the
HeAP placer and the associated Eigen3 dependency.
Default for the iCE40 is SA placer, with --heap-placer to use HeAP
Default for the ECP5 is HeAP placer, as SA placer can take 1hr+ for
large ECP5 designs and HeAP tends to give better QoR. --sa-placer can
be used to use SA instead, and auto-fallback to SA if HeAP not built.
Signed-off-by: David Shah <dave@ds0.me>
During packing we replace them by standard SB_IO cells and create the
'fake' SB_GB that matches that IO site global buffer connection.
It's done in a separate pass because we need to make sure the nextpnr iob
have been dealt first so we have our final Bel location on the SB_IO.
Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
Those are cells that are created mainly to handle the various sources a
global network can be driven from other than a user net.
When the flag is set, this means the global network usually driven by
this BEL is in fact driven by something else and so that SB_GB BEL and
matching global network can't be used.
This is also what gets used to set the extra bits during bitstream
generation.
Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
