Each table entry is made up of match fields and action data, with the
latter made up of the action ID and the action arguments. The approach
of having the user specify explicitly the endianness of the action
arguments is difficult to be picked up by P4 compilers, as the P4
compiler is generally unaware about this aspect.
This commit introduces the auto-detection of the endianness of the
action arguments by examining the endianness of the their destination:
network byte order (NBO) when they get copied to headers and host byte
order (HBO) when they get copied to packet meta-data or mailboxes.
The endianness specification of each action argument as part of the
rule specification, e.g. H(...) and N(...) is removed from the rule
file and auto-detected based on their destination. The DMA instruction
scope is made internal, so mov instructions need to be used. The
pattern of transferring complete headers from table entry action args
to headers is detected, and the associated set of mov instructions
plus header validate is internally detected and replaced with the
internal-only DMA instruction to preserve performance.
Signed-off-by: Cristian Dumitrescu <cristian.dumitrescu@intel.com>
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