make stdlib::readback work in lazy mode

[tjjfvi]

No description provided.

[HigherOrderBot]

Perf run for 51f4a77:

file              mode        main          51f4a77e48bb
========================================================
sum_rec           intr-singl      14.068 s      14.873 s
                  intr-multi       7.410 s       7.265 s
--------------------------------------------------------
bitonic_sort_lam  intr-singl      10.920 s      11.640 s
                  intr-multi       5.654 s       5.373 s
--------------------------------------------------------
merge_sort        intr-singl       7.173 s       7.603 s
                  intr-multi       3.651 s       3.699 s
--------------------------------------------------------
sum_tail          intr-singl       1.120 s       1.216 s
                  intr-multi       1.148 s       1.149 s
--------------------------------------------------------
c2                intr-singl       0.000 s       0.000 s
                  intr-multi       0.001 s       0.001 s
--------------------------------------------------------
sum_tree          intr-singl       9.092 s       9.395 s
                  intr-multi       4.427 s       4.366 s
--------------------------------------------------------
boom              intr-singl       2.263 s       2.289 s
                  intr-multi       2.590 s       2.836 s
--------------------------------------------------------
radix_sort_lam    intr-singl       9.674 s       9.584 s
                  intr-multi       4.759 s       4.776 s

[developedby]

I don't understand what is the difference between normalizing inside readback and normalizing and then calling readback.
Why was the previous one not working?

[tjjfvi]

I'm not sure what you mean.

The old readback function was designed exclusively for strict mode, and used special reference nodes to ensure the argument was normalized. This approach doesn't work on lazy mode, because the interactions with the special reference nodes will never be reached in normalization.

In lazy mode, one simply needs to call normal_from on a wire to ensure it's normalized; you don't need to do anything with special reference nodes.

This PR just makes it so that the readback function chooses between those two approaches based on M::LAZY.

[developedby]

I'm not sure what you mean.

The old readback function was designed exclusively for strict mode, and used special reference nodes to ensure the argument was normalized. This approach doesn't work on lazy mode, because the interactions with the special reference nodes will never be reached in normalization.

In lazy mode, one simply needs to call normal_from on a wire to ensure it's normalized; you don't need to do anything with special reference nodes.

This PR just makes it so that the readback function chooses between those two approaches based on M::LAZY.

I understand it now. Sorry, all this IO code is a bit hard to understand without an explanation