Episodes

  • Parsers
    Feb 23 2023
    42 mins
  • Episode 4: t-r-a-c-/e̅‾\-o-m-p-i-l-e
    May 6 2022
    Monitor. Compile. Bail. Repeat!
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    38 mins
  • Episode 3: __builtin_expect(!!(x), 0)
    Apr 19 2021

    * What is it we know statically?
    * What's effectively discoverable only at runtime?
    * How do we tell "the machine" (compiler and/or hardware):
    * Things we *know* to be true...
    * Things we *expect* to be true...
    * Things we *expect* to be true but *want to do something about* when it's not...
    * Things we have no idea about!
    * How do we collect that information that we have no idea about?
    * What happens if we're wrong? What if the workload is inherently irregular?
    * In the limit, random noise could drive our control decisions!
    * We talked a bit about precise vs imprecise exceptions before and automatic reordering, and we've mentioned vector machines and auto-vectorization.
    * All falls into the broader theme here, but we're always questioning what we can actually cover in an hour...
    * We'll try to give it a go for a subset of these things!
    * Time is often the limiting factor.

    * The episode title is the thing that we often macro define as `#define UNLIKELY`
    * In C/C++ code you might say "this control condition is unlikely", and say `if (UNLIKELY(condition))`
    * In C++20 there was added these `[[likely]]` and `[[unlikely]]` annotations that do the same thing, but with more square brackets, so clearly better!

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    39 mins
  • Episode 2: https://tlbh.it^M
    Feb 21 2021

    What happens when you type https://tlbh.it in your browser's address bar, and press enter?

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    57 mins
  • Episode 1: *(char*)0 = 0
    Nov 23 2020

    The adventure of storing NUL to NULL!

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    44 mins
  • Episode 0: mov fp, sp
    Nov 2 2020
    The stack, and how it relates to TLB Hits.
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    1 hr and 4 mins