Bug 1495 – frontend optimization

int global; void func() { global++; } alias void function() foo_t; void myfunc(int endi,int endj, foo_t argfunc) { for (int i=0;i<endi;i++) { for(int j=0;j<endj;j++) { argfunc(); } } } void main() { int i=20, j=40; myfunc(i,j, &func); printf("%d",global); } the codegen of DMD in the loop of myfunc, each time the i,j are from stack, and including incremental, and 20,40 are pushed to stack to pass to myfunc, also &func stuff. The point is here, frontend should try to template instantiate the func the frontend should try to const int i=20,j=40; to see if there's any problem, if no, then continue the optimization by making myfunc like a template, and accepting template arg to instantiate. So the i=20, j=40 stuff could be optimized, that doesn't need any push on stack. and also the func could be inlined by template instantiation.

This isn't feasible in general. But I think most of the optimisation potential in here has been addressed by pure; the compiler has much more chance to inline when it knows about pure functions.