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565 points zdw | 3 comments | 09 Jul 25 14:40 UTC | HN request time: 1.591s | source
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jcalvinowens ◴[09 Jul 25 18:21 UTC] No.44513250[source]▶
> On the one hand, compilers would like to exploit the strong guarantees of the type system—particularly those pertaining to aliasing of pointers—in order to unlock powerful intraprocedural optimizations.

How true is this really?

Torvalds has argued for a long time that strict aliasing rules in C are more trouble than they're worth, I find his arguments compelling. Here's one of many examples: https://lore.kernel.org/all/CAHk-=wgq1DvgNVoodk7JKc6BuU1m9Un... (the entire thread worth reading if you find this sort of thing interesting)

Is Rust somehow fundamentally different? Based on limited experience, it seems not (at least, when unsafe is involved...).

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1. rayiner ◴[10 Jul 25 02:53 UTC] No.44516742[source]▶
> Compiler people think aliasing matters. It very seldom does. And VLIW will never become practical for entirely unrelated reasons (read: OoO is fundamentally superior to VLIW in general purpose computing).

I love how long Linus has been right about this.

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2. saagarjha ◴[10 Jul 25 04:04 UTC] No.44517062[source]▶
He's right about OoO but not about aliasing.
3. Someone ◴[10 Jul 25 07:49 UTC] No.44518433[source]▶
Linus worked for Transmeta in 2003. That company built a VLIW CPU.

I don’t think you were a visionary if you stated VLIW is not practical for general purpose computing after that time.

Also “VLIW will never become practical” is a stronger claim than “VLIW will never become practical for general purpose computing”, and may be up for debate. https://en.wikipedia.org/wiki/Very_long_instruction_word says

“Since the number of transistors on a chip has grown, the perceived disadvantages of the VLIW have diminished in importance. VLIW architectures are growing in popularity, especially in the embedded system market, where it is possible to customize a processor for an application in a system-on-a-chip.”

That may be untrue or no longer true, but clicking around looking a the Wikipedia pages for several of the mentioned VLIW designs, I couldn’t find conclusive evidence for that (but, as with that VLIW page, the pages I looked at may be out of date, weren’t clear as to whether chips still were in production, whether newer generations actually still are VLIW, etc.)