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C++Now 2018: Matt Godbolt “What Else Has My Compiler Done For Me Lately?”

CppNow3 HN recommenders · 2018–2020
11K views · talk · evergreen · Uploaded 2018-06-07

Matt Godbolt, creator of Compiler Explorer, tours surprising optimizations modern compilers perform, such as turning loops into closed-form sums and using popcount instructions. He explores what the compiler does behind the scenes.

HN recommends it as a detailed, entertaining look at the crazy optimizations compilers do.

Compilers, interpreters & program analysisC, C++, Rust, Go & systems languagesSoftware performance & optimization

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4 comments from Hacker News

@foxrob922018 · in “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. [LINK] [VIDEO]

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@snailmailman2019 · in “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] [LINK] [1] [VIDEO]

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@drej2020 · in “Rust: Zero-Cost Abstraction in Action”

This is not Rust specific, this is a compiler thing, both LLVM and GCC can detect sums and generate closed form formulas instead. There are other fun algorithm detections - e.g. if you try to do bitcounts yourself, LLVM will use popcnt instead. Compilers are awesome, check out Matt Godbolt's talk on this very topic: [VIDEO]

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@manaskarekar2020 · in “I translated a simple C program to x86_64 and it was slower”

Tangent, but this reminds me of this great talk by Matt Godbolt from CppCon 2017: “What Has My Compiler Done for Me Lately? Unbolting the Compiler's Lid” [LINK] . And the follow up [VIDEO] .

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