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Document and adjust node struct size for better padding usage#207

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Paul1365972 wants to merge 1 commit intoMCHPR:masterfrom
Paul1365972:adjust_node_layout
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Document and adjust node struct size for better padding usage#207
Paul1365972 wants to merge 1 commit intoMCHPR:masterfrom
Paul1365972:adjust_node_layout

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@Paul1365972
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Extracted the commit from #206.

This PR documents the layout of the Node struct in the redpiler's direct backend.
Other than the explaination itself, I also applied it and found out we can just reduce the inline capacity by 1 and reduce the size of the struct by 16 bytes. The alternative would be to increase the inline capacity to 13 for free.
I went for the first option as it was closer, but I have not benchmarked anything so the second idea might be better. Although I expect the difference to be miniscule.

@StackDoubleFlow
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Yeah I benchmarked this on my Ryzen 7 7840U laptop with Iris mandlebrot (iris_test_harness) and couldn't get a measureable performance change

@Paul1365972
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Hmm I would have expected at least a minimal one, but I guess MCHPRS is not memory bottlenecked at all in its current state. I suspect a real measureable difference will only appear when the actively used subsection of Nodes either barely does or barely does not fit entirely inside inside of the L2 / L3 cache, but thats only conjecture.

In that case feel free to merge or close this issue, I have no preference either way.

@StackDoubleFlow
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I had the same conjecture, so I am also surprised. I want to do a bit more testing with this so I'll leave it open for now

@StackDoubleFlow
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Closing since forward links were moved out Node in #214

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