https://issues.dlang.org/show_bug.cgi?id=14431
Walter Bright <[email protected]> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |[email protected] --- Comment #12 from Walter Bright <[email protected]> --- (In reply to Martin Nowak from comment #7) > This slowdown comes from > https://github.com/D-Programming-Language/dmd/pull/4384, which does > instantiate additional templates in order to resolve link bugs. > The problem is amplified by using single file compilation. The trouble is the compiler would not instantiate a template if that template was already instantiated by an imported model, on the assumption that the instantiation would exist in the object code generated when the imported module was separately compiled. The problem was that if A imports B, and B imports A, A and B are compiled separately, and so the template was never instantiated (see https://issues.dlang.org/show_bug.cgi?id=2644). The 4384 fixed this by always instantiating templates if the imported module also imported root modules, as computed by TemplateInstance::needsCodegen(). The trouble with that, and the slowdown, is the commonplace practice of having every module in a project import every other module. An obvious workaround for users is to compile modules that mutually import each other on the same command to dmd. A possible solution to this was proposed by Martin Nowak: "I think we should define a rule for which module is responsible for the instantiation when they mutually import each other. I'd suggest that the module with the lexicographically smaller module name does it." --
