[almostgotcaught]

> It turns out that if you have language semantics that make optimizations hard, making a fast optimizing compiler is hard. Who woulda thunk?

Is this in the article? I don't see Python's semantics mentioned anywhere as a symptom (but I only skimmed).

> shows how poorly a lot of people understand what goes into making a language fast.

...I'm sorry but are you sure you're not one of these people? Some facts:

1. JS is just as dynamic and spaghetti as Python and I hope we're all aware that it has some of the best jits out there;

2. Conversely, C++ has many "optimizing compiler[s]" and they're not all magically great by virtue of compiling a statically typed, rigid language like C++.

[o11c]

JS is absolutely not as dynamic as Python. It supports `const`ness, and uses it by default for classes and functions.

[dontlaugh]

More importantly, there's nothing like locals[] or __getattribute__.

[pjmlp]

Smalltalk has them, and its JIT research eventually became Hotspot.

Anything can change at any time in Smalltalk.

[igouy]

And then we find out that Smalltalk implementations might choose to optimize instead of allowing anything to change at any time.

    ifFalse: alternativeBlock 
        "Answer the value of alternativeBlock. Execution does not actually
        reach here because the expression is compiled in-line."

        ^alternativeBlock value

[pjmlp]

One tree doesn't make a forest, from whatever implementation that was taken out of, and naturally there are always magician tricks that PyPy also uses.

[igouy]

*iirc* pretty much all of the Smalltalks (that was CUIS).

    ~

"Creating blocks in Smalltalk has always been a potential source of performance problems. … In Resilient, we have restricted blocks to be last in-first-out (LIFO)…"

https://blog.bracha.org/resilient-paper.pdf

    ~

"Digitalk’s Team/V unobtrusively introduced a non-reflective syntax…"

https://wirfs-brock.com/allen/posts/914

[dontlaugh]

Strongtalk limited dynamic features.

But you’re not wrong in general. Even for Python there’s PyPy, with a JIT ~3x faster than CPython.

[pjmlp]

Strongtalk was the transition step between Smalltalk JITs and what became Sun's Hotspot, but that wasn't the main point I was making.

Also to note that even in that regard, Java happens to be more dynamic that people think, while the syntax is C++ like, the platform semantics are more akin to Smalltalk/Objective-C, hence why a JIT with such a background was a great addition.

[hyperpape]

There's a pretty big gap between "its JIT research eventually became Hotspot" and "Smalltalk can be made to perform on a par with Hotspot."

[pjmlp]

HN comments usually aren't big enough for a CS lecture regarding evolution of dynamic compilation, aka JIT.

There is enough stuff to fill at least one semester.

[almostgotcaught]

yes there is: https://wiki.python.org/moin/UsingSlots

people really don't know enough about this to be talking about it with such confidence...

[dontlaugh]

I was pointing examples of the opposite, that JavaScript is less dynamic than Python.

There's lots of Python code out there that relies on not using slots. If you're making a JIT, you can't assume that all code is using slots.