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Docs: Update synth starter for check before flatten

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Krystine Sherwin 2026-05-07 17:38:30 +12:00
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24
docs/source/getting_started/example_synth.rst
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@ -291,7 +291,10 @@ In `synth_ice40` we get these:
:name: synth_flatten
:caption: ``flatten`` section
First off is `flatten`. Flattening the design like this can allow for
We start by runnning `check`. This doesn't affect the design, but it can
identify a few obvious problems which will cause errors later. Calling it here
lets us fail faster rather than wasting time on something we know is impossible.
Next up is `flatten`. Flattening the design like this can allow for
optimizations between modules which would otherwise be missed. Let's run
:yoscrypt:`flatten;;` on our design.
@ -363,17 +366,14 @@ In the iCE40 flow, we start with the following commands:
:caption: ``coarse`` section (part 1)
:name: synth_coarse1
We've already come across `opt_expr`, and `opt_clean` is the same as `clean` but
with more verbose output. The `check` pass identifies a few obvious problems
which will cause errors later. Calling it here lets us fail faster rather than
wasting time on something we know is impossible.
Next up is :yoscrypt:`opt -nodffe -nosdff` performing a set of simple
optimizations on the design. This command also ensures that only a specific
subset of FF types are included, in preparation for the next command:
:cmd:title:`fsm`. Both `opt` and `fsm` are macro commands which are explored in
more detail in :doc:`/using_yosys/synthesis/opt` and
:doc:`/using_yosys/synthesis/fsm` respectively.
We've already come across `opt_expr` and `check`, and `opt_clean` is the same as
`clean` but with more verbose output. Next up is :yoscrypt:`opt -nodffe
-nosdff` performing a set of simple optimizations on the design. This command
also ensures that only a specific subset of FF types are included, in
preparation for the next command: :cmd:title:`fsm`. Both `opt` and `fsm` are
macro commands which are explored in more detail in
:doc:`/using_yosys/synthesis/opt` and :doc:`/using_yosys/synthesis/fsm`
respectively.
Up until now, the data path for ``rdata`` has remained the same since
:ref:`rdata_flat`. However the next call to `opt` does cause a change.