macro: automatic placement with flattened synthesis

[oharboe]

If I'm to use flattened synthesis with macro placement from hierarchical synthesis, then sweeping die area values becomes tedious.

Let us see how bad macro placement is with flattened synthesis.

[oharboe]

macro placement with flattened synthesis does not look promising.

Here we can see the register files in the upper right corner and the top right macro has the pins at the top, which is a terrible placement.

Flattened synthesis with macro placement from hierarchical synthesis works much better. Here the pins for the two large register files are facing the large open area in the middle.

[oharboe]

@jeffng-or @maliberty Just FYI. An experiment to see how bad macro placement is with flattened synthesis....