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Why SSA Compilers?

(mcyoung.xyz)
182 points transpute | 1 comments | 22 Oct 25 20:13 UTC | HN request time: 0.217s | source
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zachixer ◴[22 Oct 25 22:09 UTC] No.45675783[source]▶
Every time I see a clean SSA explainer like this, I’m reminded that the “simplicity” of SSA only exists because we’ve decided mutation is evil. It’s not that SSA is simpler — it’s that we’ve engineered our entire optimization pipeline around pretending state doesn’t exist.

It’s a brilliant illusion that works… until you hit aliasing, memory models, or concurrency, and suddenly the beautiful DAG collapses into a pile of phi nodes and load/store hell.

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1. mrkeen ◴[23 Oct 25 06:34 UTC] No.45678840[source]▶
> we’ve decided mutation is evil

The functional programmers have decided mutability is evil. The imperative programmers have not.

We functional programmers do crazy stuff and pretend we're not on real hardware - a new variable instead of mutating (how wasteful!) and infinite registers (what real-world machine supports that!?).

Anyway, there's plenty of room for alternatives to SSA/CPS/ANF. It's always possible to come up with something with more mutation.