DPDK Backend: Fix binary operations with 1st operand is not same as dst operand

[usha1830]

DPDK needs the binary operation to have 1st src operand same as dst operand.
Some cases with non commutative operations were not correctly handled by the existing transformation pass.
For example:
a = b << a
should be converted to

tmp =b
tmp = tmp << a
a = tmp

[hanw]

You can save one more instruction with

a = a - 10
a = -a

[usha1830]

You can save one more instruction with

a = a - 10
a = -a

Han, the transformation also applies to other non-commutative operations like shift
I have updated the PR description to avoid confusion, will also update the code comment for this.

[hanw]

Ok, but my comment is still valid.

[mihaibudiu]

This function is actually PSA-specific, not DPDK specific. So it should probably move to some common file eventually.

[usha1830]

How about creating a utils.h/cpp under backends/common/ ?

[mihaibudiu]

We should probably move more stuff in such a place. But it should be in some directory named "psa".

[usha1830]

This specific function is for both psa and pna metadata. Of course, we can split it up if we decide to go with arch-specific common utils.
Can this PR be merged if this does not need to be an immediate action?

[usha1830]

Ok, but my comment is still valid.

Yes. Do you think, this case should be specially handled?

Also, I don't see any instruction for negation here
https://doc.dpdk.org/api/rte__swx__pipeline_8h.html#acf7715fccb903f8eca8b000953b188cb

[hanw]

Ok, but my comment is still valid.

Yes. Do you think, this case should be specially handled?

Also, I don't see any instruction for negation here https://doc.dpdk.org/api/rte__swx__pipeline_8h.html#acf7715fccb903f8eca8b000953b188cb

Thanks for the pointer. This looks fine.