Suppression Rules

The suppression rules are a YAML formatted file with the following basic form:

suppress:
  rules:
    <warning_id>:
      - msg: Port I_CLK_A not used
        comment: This port is not used in this design.
        author: jcleary
      - msg: Port I_DATA_A not used'
        comment: This port is not used in this design.
        author: jcleary
        investigate : True
    <warning_id>:
      - msg: Signal fifo_enable is tied high
        comment: The FIFO is always enabled in this design to support data throughput.
        author: jcleary
        options:
          - suppress_in_json_if_unmatched

It starts with the suppress key and then a rules key. The rules key contains one or more suppression rules. Each rules key is further divided into one or more warning ids.

Warning IDs

Regular expressons are support in warning ids. This allows for another method of grouping suppressions. In the example below, every ID that starts with Synth- and has flip-flop in the message will be suppressed.

suppress:
  rules:
    Synth-.*:
      - msg: flip-flop

Suppression Rule Fields

Each suppression rule will have the following fields available:

Option	Required	Description
msg	Yes	The message to suppress. This will be a regular a regular expression which will match after the defined message ID. LSW will prepend a .* to this field.
comment	No	While optional, it is strongly recommened to use this field to document why the warning was suppressed.
author	No	Document who created the suppression.
investigate	No	Boolean(True/False) indicating the warnings the rule suppresses need further analysis. This defaults to False.
options	No	A list of options applied to the suppression.

In addition to the standard warning ID, each tool may have warnings without IDs. When processing these warnings, ELFWS will use a warning ID of no_id.

suppress:
  no_id:
    msg: Unused port
    comment: This port is not used.
    author: mpw
  <warning_id>:
    msg: Port I_CLK not used
    comment: This port is not used.
    author: jcl

If these unique IDs exist, they are listed in the tool section of this documentation.

Grouping Rules

It can be helpful to group rules based on some criteria. For example, file names, sections in a log file, design elements or warning types.

suppress:
  <group id>:
    rules:
      <warning_id>:
        - msg: FIFO uses same clock for read and write

Arbitrary levels of groupings are also supported:

suppress:
  <group id>:
    rules:
      <warning_id>:
        - msg: FIFO uses same clock for read and write
  <group id>:
    <group id>:
      rules:
        <warning_id>:
          - msg: RAM address bits [12:3] are unused
    <group id>:
      rules:
        <warning_id>:
          - msg: invalid false path
    rules:
      <warning_id>:
        - msg: UART is blackboxed
  rules:
    <warning_id>:
      - msg:  signal fifo_wr is tied high

Dividing suppression rules into groups helps with maintaining the suppress rules. ELFWS flattens all the suppression rules into a single list.

Options

Options change the behavior of a suppression.

The following table includes all avialable options:

Option	Description
suppress_in_json_if_unmatched	The suppression will be suppressed in the json xml file only.