Mostly, this looks pretty good. Consider removing the peephole.c file altogether. It was originally part of compile.c and got separated out when it got too large. We can more the PyCode_Optimize() function back to compile.c. Ideally, we could drop it from the public api as part of Victor's PEP to overhaul the C API.

One small loss is that the current code has macros that provide meaningful opcode groupings like UNCONDITIONAL_JUMP, CONDITIONAL_JUMP, ABSOLUTE_JUMP, and JUMPS_ON_TRUE. I always found those grouping helpful for reasoning about the code.

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@rhettinger
I've removed peephole.c as you suggested.

The UNCONDITIONAL_JUMP, CONDITIONAL_JUMP, ABSOLUTE_JUMP, and JUMPS_ON_TRUE don't seem that useful in an instruction based optimizer.
I initially created versions of them, but it turned out they were unused. So I deleted them.
For jump-to-jump elimination, it turns out that the exact opcode is more important that whether a jump is conditional and/or relative.

🤖 New build scheduled with the buildbot fleet by @pablogsal for commit fda0bed 🤖

If you want to schedule another build, you need to add the ":hammer: test-with-buildbots" label again.

One final tweak. Jumps to empty blocks that were immediately followed by jumps were not being eliminated. The final commit fixes that.