On 'simple' Optimizations - Chandler Carruth - Secret Lightning Talks - Meeting C++ 2016

On "simple" Optimizations - Chandler Carruth - Secret Lightning Talks - Meeting C++ 2016

[MattGodbolt]

Wow: thanks for the amazing shout out for Compiler Explorer :)

[TheArtikae]

Update: Clang now identifies that the return value is 10!

Funnily enough, if you don’t specify v.reserve(4), you still get an allocation, but the allocation is totally unused. It calls operator new, then operator delete, then returns 10.

[pfeilspitze]

Did you know that searching for "the number of inlining shall be three" finds Monty Python videos, not this one?

[kamilziemian]

I really like Chandler Carruth's talks.

[SolomonUcko]

Moral: run your optimizer repeatedly until the code is optimized enough ;)

[MrAbrazildo]

Maybe you should create even more flags for the compiler. Not to throw all of them at the user's face, but to have flags that can "unlock" new options/flags, if the user is trying to go deeply in optimization.
Just an idea.

[xealit]

Optimizer indeed should be able to optimize out such a trivial example with literal input in the program source etc. But what's the point? In reality, such examples probably show up only in some simple toy-benchmarks.

[johnbaxter]

I like the idea of the optimiser going out to launch 😆

[rubberduck]

here's how you optimize for less alllocations: don't write code that does many allocations

[iddn]

I don't see why the compiler would be expected to optimize that out. Sure, the return value is one thing but someone may actually want the heap allocation side effects

[dengan]

Soooo basically it is a rant because the compiler doesn't *acually* runs your code and hard-code into resulting executable? .. interesting

[rubberduck]

Why should this be optimized? It shouldn't.