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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. whitequark‏ @whitequark Mar 25
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      hot take: if C++ was truly committed to zero cost abstractions, functions would have opt-in reentrancy, the same way classes have opt-in vtables

      18 replies 17 retweets 194 likes
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    2. Patrick Walton‏ @pcwalton Mar 25
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      Replying to @whitequark

      I seem to recall Knuth said ALGOL (was it?) would never be fast enough for this exact reason

      1 reply 0 retweets 3 likes
    3. Vertigo‏ @SamuelAFalvoII Mar 25
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      Replying to @pcwalton @whitequark

      I think it's important to remember that the reason early compilers differentiated between recursive and non-recursive functions is because early processors lacked a push-down stack.

      1 reply 2 retweets 1 like
    4. Vertigo‏ @SamuelAFalvoII Mar 25
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      Replying to @SamuelAFalvoII @pcwalton @whitequark

      If you called a subroutine at address A, the return PC would literally be stored at A, and the first instruction of the subroutine would start at A+1. Such processors were still the state of the art when Algol was conceived.

      2 replies 2 retweets 3 likes
    5. whitequark‏ @whitequark Mar 25
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      Replying to @SamuelAFalvoII @pcwalton

      i did learn that while writing an llvm backend for pdp-7. however. you could definitely make a compiler targeting pdp-7 that would have all procedures reentrant, it'd just be slow.

      2 replies 0 retweets 3 likes
      Patrick Walton‏ @pcwalton Mar 25
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      Replying to @whitequark @SamuelAFalvoII

      CC65 works this way I think. You pretty much have to static all your local variables or your performance craters.

      10:20 PM - 25 Mar 2020
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      • Dusk 💛 💜 Hazelesque Vertigo whitequark
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        2. Vertigo‏ @SamuelAFalvoII Mar 25
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          Replying to @pcwalton @whitequark

          For a long while, being a massive Forth entheusiast, I thought Forth was something of a local optimum for languages targeting early 8-bit CPUs. But, I'm beginning to realize that's not the case; believe it or not, it's compiled BASIC that is the local optimum.

          1 reply 0 retweets 2 likes
        3. Vertigo‏ @SamuelAFalvoII Mar 25
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          Replying to @SamuelAFalvoII @pcwalton @whitequark

          And the reason is exactly what you mentioned above: stack accesses are just plain expensive (even push and pop!) compared to a straight absolute memory reference. And with BASIC's general lack of local variables, all you *have* are global/absolute memory references. :)

          0 replies 0 retweets 4 likes
        4. End of conversation

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