On 2016-09-11 23:48, Stefan Koch wrote:
Hi,
As you may know I am currently optimizing template-related code inside
of DMD.
Inside DMD code quality is quite high, there is little low hanging fruit.
However there is one thing that suspiciously often shows up the on
profilers display.
Those are indirect class which have a high number of L2(!) i-cache misses.
These calls don't do a lot of work. They are needed either for downcasts
or to verify the dynamic type of an AST-Node.
Even without the i-cache related stalls the call overhead alone is
something to think about.
For template-heavy code matching template parameters is one of the most
frequently operations.
Since Template Parameters can be types expressions or symbols the
dynamic-types are heavily queried.
First experiments suggest that a speedup of around 12% is possible if
the types where accessible directly.
Since dmd uses visitors for many things now the benefit of virtual
methods is highly reduced.
Please share your thoughts.
What about using an enum in the base class that indicates the runtime
type? The Expression class is already using this technique. Add it to
Declaration and Statement as well, or even to RootObject.
--
/Jacob Carlborg
