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0 pointsgpderetta5y ago0 comments

I think the point of the parent is that in principle you can always implement those optimizations by hand in C although it might of course be impractical.

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bhaak5y ago

If you go down this road then you can always drop down to assembler to be even faster than C.

I don't think this is a reasonable argument. Every Turing compatible language that gives you direct access to the metal, so to speak, provides you with the opportunity to implement these optimization by hand.

I think it's much better to look at average C code there. And then C has a tremendous advantage with their compiler support. C compilers have decades of optimization put into them. This will take a while for other languages to catch up to that.

WalterBright5y ago

The three D compilers use, the GCC backend, the LLVM backend, and the Digital Mars backend. All the decades of optimization in them are taken advantage of by D. If you write C-style code in D, you'll get the same code generated as if your wrote it in C.

bhaak5y ago

But isn't that a consequence of D "mimicking" C to some extent?

Disclaimer, my compiler background was the Java compiler and its bytecode generation but I would expect both gcc and clang/llvm to have lots of optimization cruft hardcoded for how C programs are written. If you deviate from that, you get potentially less well optimized code.

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WalterBright5y ago

> in principle you can always implement those optimizations by hand in C

Some things, like integral promotion rules, you can't get around. You may know that the promotion can be skipped in certain cases, but the compiler cannot know it.

j / k navigate · click thread line to collapse

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bhaak5y ago

If you go down this road then you can always drop down to assembler to be even faster than C.

WalterBright5y ago

bhaak5y ago

But isn't that a consequence of D "mimicking" C to some extent?

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WalterBright5y ago

> in principle you can always implement those optimizations by hand in C

Some things, like integral promotion rules, you can't get around. You may know that the promotion can be skipped in certain cases, but the compiler cannot know it.

j / k navigate · click thread line to collapse