On Tuesday, 18 August 2015 at 10:45:49 UTC, Walter Bright wrote:
So if you're comparing code generated by dmd/gdc/ldc, and
notice something that dmd could do better at (1, 2 or 3),
please let me know. Often this sort of thing is low hanging
fruit that is fairly easily inserted into the back end.
I have a about 30 lines of numerical code (using real) where the
gap is about 200%-300% between ldc/gdc and dmd (linux x86_64). In
fact dmd -O etc is at the level of ldc/gdc without any
optimizations and dmd without -0 is even slower.
With double instead of real the gap is about 30%.
dmd is unable to inline 3 function calls (pragma(inline, true) =>
compiler error) but for ldc disabling inlining does not really
hurt performance.
My knowledge of asm and compiler optimizations are quite limited
and I can't figure out what dmd could do better.
If someone is interested to investigate this, I can put the
source + input file for the benchmark on github. Just ping me:)
Notice: I use ldc/gdc anyway for such stuff and imo the
performance of dmd is not the most important issue with D - e.g.
compared to C++ interface (mainly std::vector).
