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Merge pull request #5858 from YosysHQ/krys/check_before_flatten

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Docs: Update synth starter for check before flatten
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KrystalDelusion 2026-05-08 02:31:03 +00:00 • committed by GitHub
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docs/source/getting_started/example_synth.rst
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@ -291,7 +291,10 @@ In `synth_ice40` we get these:
:name: synth_flatten :name: synth_flatten
:caption: ``flatten`` section :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 optimizations between modules which would otherwise be missed. Let's run
:yoscrypt:`flatten;;` on our design. :yoscrypt:`flatten;;` on our design.
@ -363,17 +366,14 @@ In the iCE40 flow, we start with the following commands:
:caption: ``coarse`` section (part 1) :caption: ``coarse`` section (part 1)
:name: synth_coarse1 :name: synth_coarse1
We've already come across `opt_expr`, and `opt_clean` is the same as `clean` but We've already come across `opt_expr` and `check`, and `opt_clean` is the same as
with more verbose output. The `check` pass identifies a few obvious problems `clean` but with more verbose output. Next up is :yoscrypt:`opt -nodffe
which will cause errors later. Calling it here lets us fail faster rather than -nosdff` performing a set of simple optimizations on the design. This command
wasting time on something we know is impossible. 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
Next up is :yoscrypt:`opt -nodffe -nosdff` performing a set of simple macro commands which are explored in more detail in
optimizations on the design. This command also ensures that only a specific :doc:`/using_yosys/synthesis/opt` and :doc:`/using_yosys/synthesis/fsm`
subset of FF types are included, in preparation for the next command: respectively.
: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 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. :ref:`rdata_flat`. However the next call to `opt` does cause a change.