[0/7] pipeline: support direct registers and meters

  This patch introduces support for direct registers and meters. The
difference between indirect (indexed) and direct registers and meters
is explained below [1][2][3].

1. Indirect (indexed) registers and meters.

The index into an array of registers or meters used on the data path
is typically read from the action data identified by a table lookup
operation.

This means that the control plane manages the mapping of the mapping
of array entries to table entries and sets up this index explicitly
into the table entry action data.

These are called indirect or indexed registers and meters, and they
allow multiple table entries to share the same register/meter, as well
as a 1:1 mapping of table entries to register/meter array entries.

2. Direct registers and meters.
In the case of 1:1 mapping of table entries to register/meter array
elements, it is sometimes desired to avoid the explicit allocation of
register/meter array index to each table entry by the control plane.

One way this can be done is by implementing a mechanism to associate
a unique ID to each table entry, including the default table entry as
well; once the entry ID is retrieved as result of the table lookup
operation, it is saved by the pipeline and used later on as the
index into the register/meter array.

These are called direct registers and meters, and have the advantage
that the index is auto-generated, which simplifies the controller
implementation; the disadvantage is that they do not allow multiple
table entries to share the same register or meter.

References:

[1] Indirect and direct counters:
https://p4.org/p4-spec/docs/PSA.html#sec-counters

[2] Indirect and direct registers:
https://p4.org/p4-spec/docs/PSA.html#sec-registers

[3] Indirect and direct meters:
https://p4.org/p4-spec/docs/PSA.html#sec-meters

Cristian Dumitrescu (7):
  table: add entry ID for regular tables
  table: add entry ID for learner tables
  pipeline: add table entry ID read instruction
  pipeline: support direct registers on the control path
  pipeline: support direct meters on the control path
  examples/pipeline: add CLI commands for direct registers
  examples/pipeline: add CLI commands for direct meters

 examples/pipeline/cli.c                  | 642 ++++++++++++++++++-----
 examples/pipeline/examples/meter.cli     |   2 +-
 lib/pipeline/rte_swx_ctl.h               | 133 +++++
 lib/pipeline/rte_swx_pipeline.c          | 349 ++++++++++++
 lib/pipeline/rte_swx_pipeline_internal.h |  21 +
 lib/pipeline/version.map                 |   5 +
 lib/table/rte_swx_table.h                |  13 +
 lib/table/rte_swx_table_em.c             |   5 +
 lib/table/rte_swx_table_learner.c        |  13 +-
 lib/table/rte_swx_table_learner.h        |  12 +
 lib/table/rte_swx_table_wm.c             |   2 +
 11 files changed, 1053 insertions(+), 144 deletions(-)