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Go Optimization Guide

(goperf.dev)
480 points jedeusus | 1 comments | 31 Mar 25 20:29 UTC | HN request time: 0s | source
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dennis-tra ◴[01 Apr 25 12:15 UTC] No.43545831[source]▶
Can someone explain to me why the compiler can’t do struct-field-alignment? This feels like something that can easily be automated.
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CamouflagedKiwi ◴[01 Apr 25 12:20 UTC] No.43545865[source]▶
Because the order of fields can be significant. It's very relevant for syscalls, and is observable via the reflect package; it'd be strange if the field order was arbitrarily changed (and might change further between releases).

I assume the thinking was that this is pretty easy to optimise if you care, and if it's on by default there'd then have to be some opt-out which there isn't a good mechanism for.

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kbolino ◴[01 Apr 25 12:31 UTC] No.43545977[source]▶
In particular, struct field alignment matches C (even without cgo) and so any change to the default would break a lot of code.
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1. int_19h ◴[01 Apr 25 22:47 UTC] No.43552073[source]▶
This is very unfortunate, since most structs are never going to be passed to C, yet end up paying the tax anyway. They really should have made it opt-in.