On Thursday, 26 July 2012 at 18:59:14 UTC, Jonathan M Davis wrote:
Clearly -O is where the big runtime speed difference is at
between dmd and gdc,
which _is_ a bit obvious, but I'm surprised that -inline had no
differences,
since dmd is generally accused at being poor at inlining. That
probably just
indicates that it's a frontend issue (which I suppose makes
sense when I think
about it).
GDC probably performs inlining by default on -O2/-O3, just like
LDC does.
Also note that for the -release case (any performance
measurements without it are most probably not worth it due to all
the extra _d_invariant, etc. calls), -inline seems to increase
the runtime of the DMD-produced executable by 10%. For inlining,
you inevitably have to rely on heuristics, and there will always
be cases where it slows down execution (worst case: the slight
improvement in code size causes cache thrashing in a hot path),
but 10% in a fairly standard application seems to be quite a lot.
David
