On Tuesday, May 16, 2017 at 8:34:43 PM UTC+8, Jochen Eisinger wrote: > > Thanks for the summary! > > I'm wondering whether you also plan other refactoring work for V8? >
No, I only have plan for this refactoring for now. > > Also, why not just import base::Bind and friends from Chromium? > Chromium's implementation uses many other Chromium-specific features like weak_ptr<>, we might end up introducing more code than V8 actually needs. As far as I can see, CodeAssemblerCallback seems to be the only use case of std::function that might benefit from Chromium's Callable<>. > > On Tue, May 16, 2017 at 2:04 PM <[email protected] <javascript:>> wrote: > >> Hi V8 devs, >> >> I saw a few functions in src/builtin/builtin-*-gen.cc and >> src/code-stub-assembler.h uses quite a few std::function as a parameter, >> then pass lambda function to these functions to avoid code duplication as >> much as possible. std::function was used because raw function pointer can't >> accept lambda function. >> >> However, because std::function is really powerful, it comes with a cost >> in terms of code size and overhead when calling std::function. >> >> I am working on introducing function_view to src/base, a lightweight >> callable reference that can accept normal and lambda function. >> >> function_view is adapted from [1] >> <https://vittorioromeo.info/index/blog/passing_functions_to_functions.html>. >> I have changed it so that it can be compiled with C++11, which is the >> minimum compiler support requirement to build Chromium. >> >> Note: >> >> The callable itself must be alive longer or equal to the life time of >> function_view object. Therefore, function_view is not a universal >> replacement for the general-purpose std::function. >> >> If you need to store lambda function as class property, std::function is >> still needed. Use case like [2] >> <https://cs.chromium.org/chromium/src/v8/src/compiler/code-assembler.h?type=cs&l=601> >> >> cannot be replaced with function_view. >> >> Chromium do have a very powerful library to store callback at >> https://cs.chromium.org/chromium/src/base/bind_internal.h (std::function >> is banned in Chromium). >> >> Plan: >> >> - Add base::function_view implementation to src/base/functional.h >> - Convert std::function to base::function_view in >> src/builtin/builtin-*-gen.cc and maybe other parts of src/* if >> appropriate. >> Usage of std::function in test/* will be ignored. >> - Add documentation. >> - Add unittest. >> >> src/compiler/s390/instruction-selector-s390.cc also uses a lot of >> std::function + lambda, but because I can't test on this platform myself, I >> don't feel safe to change it. It looks like dry run does not have bot for >> s390. >> >> WIP CL: >> >> https://chromium-review.googlesource.com/c/505653/ >> >> [1]: >> https://vittorioromeo.info/index/blog/passing_functions_to_functions.html >> [2]: >> https://cs.chromium.org/chromium/src/v8/src/compiler/code-assembler.h?type=cs&l=601 >> >> Sincerely, >> Rong Jie >> > -- -- v8-dev mailing list [email protected] http://groups.google.com/group/v8-dev --- You received this message because you are subscribed to the Google Groups "v8-dev" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
