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Merge pull request #1661 from YosysHQ/eddie/abc9_required

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abc9: add support for required times
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Eddie Hung 2020-02-05 18:59:40 +01:00 • committed by GitHub
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@ -373,10 +373,15 @@ Verilog Attributes and non-standard features
`abc9` to preserve the integrity of carry-chains. Specifying this attribute
onto a bus port will affect only its most significant bit.
- The port attribute ``abc9_arrival`` specifies an integer (for output ports
only) to be used as the arrival time of this sequential port. It can be used,
for example, to specify the clk-to-Q delay of a flip-flop for consideration
during `abc9` techmapping.
- The output port attribute ``abc9_arrival`` specifies an integer, or a string
of space-separated integers to be used as the arrival time of this blackbox
port. It can be used, for example, to specify the clk-to-Q delay of a flip-
flop output for consideration during `abc9` techmapping.
- The input port attribute ``abc9_required`` specifies an integer, or a string
of space-separated integers to be used as the required time of this blackbox
port. It can be used, for example, to specify the setup-time of a flip-flop
input for consideration during `abc9` techmapping.
- The module attribute ``abc9_flop`` is a boolean marking the module as a
flip-flop. This allows `abc9` to analyse its contents in order to perform