On Monday, 9 May 2016 at 16:57:39 UTC, Stefan Koch wrote:
Hi Guys,
I have been looking into the DMD now to see what I can do about
CTFE.
Unfortunately It is a pretty big mess to untangle.
Code responsible for CTFE is in at least 3 files.
[dinterpret.d, ctfeexpr.d, constfold.d]
I was shocked to discover that the PowExpression actually
depends on phobos! (depending on the exact codePath it may or
may not compile...)
which let to me prematurely stating that it worked at ctfe
[http://forum.dlang.org/thread/[email protected]]
My Plan is as follows.
Add a new file for my ctfe-interpreter and update it gradually
to take more and more of the cases the code in the files
mentioned above was used for.
Do Dataflow analysis on the code that is to be ctfe'd so we can
tell beforehand if we need to store state in the ctfe stack or
not.
Or baring proper data-flow analysis: RefCouting the variables
on the ctfe-stack could also be a solution.
I will post more details as soon as I dive deeper into the code.
What is the current problem with ctfe?
Before I switched from C++ to D a few months ago I was heavily
using boost hana in C++. I tried to emulate hana in D which
worked quite well but the compile time performance was absolutely
horrific
https://maikklein.github.io/2016/03/01/metaprogramming-typeobject/
After that I tried a few other things and I compared the compile
times with
https://github.com/boostorg/hana/tree/master/benchmark
which I could never beat. The fastest thing, if I remember
correctly, was string mixins but they used up too much memory.
But I have to say that I don't know much about the D internals
and therefore don't know how I would optimize ct code execution.
