gh-104909: Implement conditional stack effects for macros by gvanrossum · Pull Request #105748 · python/cpython
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Currently only conditional output effects in the last sub-instruction are supported.
This is needed so we can make progress with splitting opcodes into uops with at most one cache entry or oparg -- some of the opcodes that need splitting have a conditional output effect.
(In last op only; and no conditional input effects.)
| src: StackEffect | None, | ||
| *, | ||
| # Don't initialize from dst.cond; used for conditional *outputs*. | ||
| unconditional: bool = False, |
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I'm finding it hard to track the directions of the different booleans here (unconditional is used for conditional outputs, and we don't initialise when it is True..).
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That's fair. I'm reverting the sense and renaming it to init_null, with a default of True (since that's what's needed in 5 out of 6 call sites).
Further testing shows the stack adjustment is not always correct.
Also remove dummy diff argument to stack_adjust().
I'll undraft this once gh-105788 is merged (which is one of the earlier commits in this PR, but should be separated out).
