[WalterBright]

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.

[bhaak]

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.

[WalterBright]

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

It's true that multi-language backends will inevitably cater to the semantics of the dominant language.

For a related example, I discovered that gdb doesn't pay much attention to the DWARF symbolic debug spec. It pays attention to the particular way gcc generates symbolic debug info. Other patterns, while compatible with the spec, don't work with gdb. Similar problems have happened with linkers.

It's a matter of "do as I do, not as I say".

Since I am the author of DMD's backend, I've been putting in optimizations that do cater to D, rather than just C and C++. For example, in the last few days I started putting in optimizations to take advantage of D's new "bottom" type:

https://github.com/dlang/dmd/pull/12245