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Frame from CppCon 2017: Matt Godbolt “What Has My Compiler Done for Me Lately? Unbolting the Compiler's Lid” Plays via YouTube's privacy-enhanced embed

CppCon 2017: Matt Godbolt “What Has My Compiler Done for Me Lately? Unbolting the Compiler's Lid”

48 videos recommended on HN
YouTube
7 HN users recommended this talk6 months2018–2022 score 7
Years with an HN recommendation, 2007–2026

HN recommends it as an entertaining, mind-blowing look at compiler cleverness from a great speaker.

Matt Godbolt's CppCon 2017 talk shows what modern compilers do with your C++ code, using Compiler Explorer to inspect generated assembly. It covers surprising optimizations and how the tool works.

“Both are great presentations going into details on some of the crazy optimizations compilers will do.” (HN, 2019)

2 strong recommendations · 6 recommendations · 4 citations · Talks · intermediate

12 Hacker News comments

From the HN archive; up to 20 kept per video, favoring different commenters. Recommendations first.

@drej Dec 2018 Strongly recommends
on HN thread Compiler Explorer
Matt Godbolt is a great speaker as well. I loved this talk that included a bit about the architecture behind his Compiler Explorer. The rest of his talk is super cool as well. E.g. closed form solutions from O(n) code? Compilers are awesome. [this video]
Great speaker covering Compiler Explorer architecture and compiler tricks.
@snailmailman Sep 2019 Strongly recommends
on HN thread Popcount CPU instruction
I highly recommend Matt Godbolt's talk "What has my compiler done for me lately?"[0] and its follow-up[1]. Both are great presentations going into details on some of the crazy optimizations compilers will do. As someone who knows very little about the inner workings of compilers my mind was blown when I saw some them. [0] [this video] [1] [link]
Mind-blowing compiler optimizations explained in detail.
@pkaye Jan 2018 Recommends
on HN thread Outperforming LAPACK with C++ metaprogramming
You should check out this presentation done by Matt Godbolt about compiler internals. He talks about what kind of optimizations are being done by GCC and Clang. Pretty amazing stuff. For example, the compiler will figure out you are trying to write a pop count in high level code and replace it with a single popcount instruction. [this video]
Shows surprising compiler optimizations in GCC and Clang, like popcount.
@drej Oct 2018 Recommends
on HN thread C++: Associative map containers with compile-time lookup
CppCon has super interesting content. That comes from a person who has written maybe two dozen lines of C++ code, mostly just hello world. E.g. this talk by Matt Godbolt or anything by Chadler Carruth. [this video]
Interesting CppCon talk even for non-C++ programmers.
@fps_doug Sep 2019 Recommends
on HN thread Color Emulation
But please keep in mind that today's compilers are (most of the time) very smart. Hacker's Delight is somewhat outdated today. There's no need anymore for writing "x << 2" instead of "x * 4". I recommend Matt Godbolt's Talk(s) about compiler cleverness: [this video] (see the 30 minute mark for the multiplication example)
Shows how clever compilers are, including multiplication optimizations.
@s3cur3 Mar 2021 Recommends
on HN thread Performance comparison: counting words in Python, Go, C++, C, Awk, Forth, Rust
Link to the (great) CppCon talk: [this video] The one thing I would say is: as you dig more into C++ perf, you can develop an intuition for the kinds of things the compiler can and can't optimize. For instance, the C++ example from the article uses `std::unordered_map`, which is just an absolute mess from a cache locality perspective—the best compilers today (or of the foreseeable future) can't do a thing to fix that. Improving the programmer's choice of data structure is just not on the radar. :(
Great CppCon talk on what compilers can optimize.

Citations, criticism and jokes

@foxrob92 Dec 2018 Cites it
on HN thread Compiler Explorer
Doesn't look like it works any more. In any case, Matt Godbolt has spoken a bit about the architecture of Compiler Explorer. Seems like he's given some thought to security. [this video] [link]
Godbolt describes Compiler Explorer's architecture and security thinking.
@bluecheese33 Sep 2019 Cites it
on HN thread Popcount CPU instruction
There's a neat example in [1] where clang replaces a loop summing integers 0..i with the closed form version. [1] [this video]
Example of clang turning a summation loop into a closed form.
@drej Aug 2020 Cites it
on HN thread Compiler Explorer
If you are wondering how it works, here is Matt Godbolt himself explaining it. Surprisingly simple and cheap. [this video]
Godbolt explains how Compiler Explorer works.
@Simran-B Oct 2022 Cites it
on HN thread Compiler Explorer
It's the CppCon 2017 talk with the title "What has my compiler done for me lately? Unbolting the compiler's lid". The Compiler Explorer backstory starts here: [this video]
Where the Compiler Explorer backstory begins.

Video list and Hacker News comment labels from HackerTube (prompted by @karpathy), released under ODC-By 1.0, built on the open-index/hacker-news archive. Hacker News data is provided by Y Combinator; comments remain the work of their authors. Video titles, channel names and thumbnails belong to their creators and are shown via YouTube. HackerTube Watch is an unofficial edition. Data export of 2026-10-31.

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