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pcwalton's profile
Patrick Walton
Patrick Walton
Patrick Walton
@pcwalton

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Patrick Walton

@pcwalton

Research engineer at Mozilla

San Francisco, CA
pcwalton.github.io
Joined November 2009

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    1. Joe Groff‏ @jckarter 4 Aug 2018
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      Replying to @jckarter @pcwalton @gparker

      Well enough that tricks that increase local code size or memory usage aren’t worth the systemwide costs, at least

      1 reply 0 retweets 0 likes
    2. Patrick Walton‏ @pcwalton 4 Aug 2018
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      Replying to @jckarter @gparker

      That would imply that JS inline caches aren't worth it. I'm skeptical, given that it's completely impossible to write a competitive JS engine without them.

      3 replies 0 retweets 1 like
    3. Patrick Walton‏ @pcwalton 4 Aug 2018
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      Replying to @pcwalton @jckarter @gparker

      I mean, it seems obvious that you will sometimes benefit from ICs, so the question is only what threshold you want to kick in the optimization at (via PGO), not whether you should do it at all.

      1 reply 0 retweets 0 likes
    4. Greg Parker‏ @gparker 5 Aug 2018
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      Replying to @pcwalton @jckarter

      Profitable PGO thresholds are one problem. Another problem is that PGO and the associated performance measurement and feedback apparatus is not yet solved, as far as I know.

      1 reply 0 retweets 0 likes
    5. Joe Groff‏ @jckarter 5 Aug 2018
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      Replying to @gparker @pcwalton

      Culturally I think ObjC programmers also tend to hand-optimize the hot parts of their code, either by not using messages at all or manually caching IMPs

      2 replies 0 retweets 6 likes
    6. Marcel Weiher  🇪🇺‏ @mpweiher 5 Aug 2018
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      Replying to @jckarter @gparker @pcwalton

      Yep. People forget the Objective-C is a hybrid language, and the idea is to have fairly coarse-grain Software-ICs implemented in C, connected via message-sends. Also, object allocation, call/return style and keyed-accessing in all its forms are magnitude(s) worse than msg-send.

      2 replies 0 retweets 3 likes
    7. Christoffer Lernö‏ @nuoji 5 Aug 2018
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      Replying to @mpweiher @jckarter and

      Unfortunately the community got saturated with C++/Java people who never grokked that idea. Thus we have Swift.

      1 reply 0 retweets 1 like
    8. Marcel Weiher  🇪🇺‏ @mpweiher 5 Aug 2018
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      Replying to @nuoji @jckarter and

      Though admittedly the Smalltalk folks also don't really get the hybrid model. And of course a "pure" programming model is attractive for many reasons. I think applying OO-techniques to our language meta-model actually allows us to have the best of both worlds.

      2 replies 0 retweets 0 likes
    9. Patrick Walton‏ @pcwalton 5 Aug 2018
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      Replying to @mpweiher @nuoji and

      Note that ICs were developed as the solution to this problem in Self/Smalltalk. They’re pretty much the only way to make dynamically typed virtual dispatch fast.

      1 reply 0 retweets 0 likes
    10. Marcel Weiher  🇪🇺‏ @mpweiher 5 Aug 2018
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      Replying to @pcwalton @nuoji and

      I am aware of the history, but this is not true: (a) granularity control in a hybrid also solves this and (b) dynamic dispatch just isn't that much of a problem any more. We lose orders of magnitude more elsewhere for much less gain.

      2 replies 0 retweets 0 likes
      Patrick Walton‏ @pcwalton 5 Aug 2018
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      Replying to @mpweiher @nuoji and

      That is totally contrary to every JS engine’s experience.

      10:37 AM - 5 Aug 2018 from Dogpatch, San Francisco
      2 replies 0 retweets 0 likes
        1. New conversation
        2. Patrick Walton‏ @pcwalton 5 Aug 2018
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          Replying to @pcwalton @mpweiher and

          Try to beat V8 or SpiderMonkey with an objc_msgSend like implementation. You won’t be able to do it.

          1 reply 0 retweets 0 likes
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