[cfe-dev] Remove unused types from ASTContext
mateusz janek via cfe-dev
cfe-dev at lists.llvm.org
Sun Apr 30 16:12:27 PDT 2017
Thanks again. Unfortunately I think that even "only AST" will be to much
for my RAM.
I have one more idea, please tell me if this makes any sense. I'm thinking
about storing class specializations in term of scopes.
(It don't want this to work with every C++ project, I'm ok with that it'll
work only with my project)
(And I'd stick to couple of assumptions during ctai implementation, e.g.
only one depth scope resolution, A::B)
(I'm aware that probably I'd need to write my own implementation of
ClassTemplateSpecializationDecl and couple of more classes)
Example code and the flow:
template <int N>
struct N_Holder
{
static constexpr int N_Value = N;
};
template <int Val1, int Val2>
struct Add_impl
{
using Val1_Holder = Holder<Val1>;
using Val2_Holder = Holder<Val2>;
static constexpr int Result_impl = Val1_Holder::N_Value +
Val2_Holder::N_Value;
};
template <int Val1, int Val2>
struct Add
{
static constexpr int Result = Add_impl<Val1, Val2>::Result_impl;
};
struct A_Struct
{
static constexpr int Value = Add<10, 20>::Result;
};
Flow:
(...)
-see class A_Struct
-go into A_Struct scope
-see a member Value =
-create class Add<10, 20> specialization
-go into Add<10, 20> scope
-see parameters {non-type 10, non-type 20}
-see member Result =
-create Add_impl<parameters[0], parameters[1]> specialization
-go into Add_impl<10, 20> scope
-see parameters {non-type 10, non-type 20}
-see alias Val1_Holder =
-create Holder<parameters[0]> specialization
-go into Holder<10> scope
-see parameters {non-type 10}
-see member N_Value = parameters[0]
-go out of Holder<10> scope (nothing do delete)
-assign Val1_Holder = Holder<10> specialization 'by value':
{
aliases {}
members { N_Value = 10 }
}
-delete Holder<10> specialization
-see alias Val2_Holder =
-create Holder<parameters[1]> specialization
-go into Holder<20> scope
-see parameters {non-type 20}
-see member N_Value = parameters[0]
-go out of Holder<20> scope (nothing do delete)
-assign Val2_Holder = Holder<20> specialization 'by value':
{
aliases {}
members { N_Value = 20 }
}
-delete Holder<20> specialization
-see member Result_impl = Val1_Holder::N_value + Val2_Holder::N_Value;
-go out of Add_impl<10, 20> scope:
-assign Result = Add_impl<10, 20>::Result_impl
-delete Add_impl<10, 20> specialization
-go out of Add<10, 20> specialization
-assign Value = Add<10, 20>::Result
-delete Add<10, 20> specialization
-go out of A_Struct scope
(...)
Thanks,
Stryku
2017-04-30 23:00 GMT+02:00 mats petersson <mats at planetcatfish.com>:
> Like I said, you need those types for most of the compilation process.
> It's REALLY hard to keep track of when these things don't matter any longer
> - you certainly need types that actually generate code all the way to
> LLVM-IR generation. That's for the AST types. IR types, which isn't quite
> the same thing.
>
> The latter, you can do by doing "syntax-only" run on the compiler - it
> won't generate any LLVM-IR, so memory usage here is "only" AST. Also,
> prodcuing LLVM-IR output from the compiler (-S -emit-llvm) and then using
> `llc` to compile the IR to machine code, to determine memory usage of the
> IR types (obviously with other things).
>
> [In my compiler project, I decided it's so hard to track what is needed
> again and what isn't, and decided to NOT free any memory for that reason -
> of course, not a particularly great strategy if you want to run it as a
> library in something else, but if I really had to, I could probably stick
> every object in one or more container(s) and free it all at the end]
>
> --
> Mats
>
> On 30 April 2017 at 21:12, mateusz janek <stryku2393 at gmail.com> wrote:
>
>> Sorry for no response, I was quite busy.
>>
>> Thanks Brian for help with the build (: Also I've tried with the g++-6
>> and it has same problem with the memory usage.
>>
>> The problem here is caused by creating a lot of template class
>> specializations. As Mats partially said and I found in the llvm sources
>> here: https://github.com/stryku/llvm/blob/master/include/llvm/IR/
>> Type.h#L42 types are stored till the end of program life. AFAIU every
>> class specialization is a separate type.
>>
>> Simpler program that shows my problem is e.g. https://gist.github.com/s
>> tryku/986bcd6a5d5773ef0e0136a5eca97e20
>> There is a lot of specializations of values_container, create_container, create_impl
>> etc. Additionally every values_container have a lot of template
>> parameters which in fact are also types (built-in types, but still).
>>
>> For now, I'm playing with llvm and clang sources to understand what's
>> going on there and I'll probably try to implement my own mechanism of
>> storing a template class specializations.
>>
>> Thanks for your interest,
>> Stryku
>>
>>
>>
>> 2017-04-29 0:02 GMT+02:00 Brian Cain <brian.cain at gmail.com>:
>>
>>>
>>> On Fri, Apr 28, 2017 at 6:11 AM, mateusz janek <stryku2393 at gmail.com>
>>> wrote:
>>>
>>>> Did you use CMake? If no, ctai requres clang 4.0 and to be compiled
>>>> with flags: `-std=c++1z -ftemplate-backtrace-limit=0
>>>> -ftemplate-depth=8096`
>>>>
>>>>
>>> I got it to work with some tweaks to the CMake config. It ran quickly
>>> for me, but it did allocate a decent amount of memory on the way. Also I
>>> used a nightly build of clang and libc++ (and not libstdc++).
>>>
>>> 15.85user 0.48system 0:16.38elapsed 99%CPU (0avgtext+0avgdata
>>> 4053852maxresident)k
>>> 0inputs+24outputs (0major+381214minor)pagefaults 0swaps
>>>
>>>
>>>
>>> diff:
>>>
>>> diff --git a/CMakeLists.txt b/CMakeLists.txt
>>> index 0143461..109d975 100644
>>> --- a/CMakeLists.txt
>>> +++ b/CMakeLists.txt
>>> @@ -1,9 +1,9 @@
>>> cmake_minimum_required(VERSION 3.5)
>>> project(ctai)
>>>
>>> -add_definitions(-std=c++1z -ftemplate-backtrace-limit=0
>>> -ftemplate-depth=1024)
>>> -
>>> -set(CMAKE_CXX_COMPILER clang++-3.9)
>>> +set(CMAKE_CXX_COMPILER clang++-3.9 CACHE STRING "")
>>> +set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++1z -stdlib=libc++
>>> -ftemplate-backtrace-limit=0 -ftemplate-depth=8192" CACHE STRING "" FORCE)
>>> +set(CMAKE_MODULE_LINKER_FLAGS ${CMAKE_MODULE_LINKER_FLAGS} "-std=c++1z
>>> -stdlib=libc++" CACHE STRING "" FORCE)
>>>
>>> set(INCLUDE_FILES
>>> register.hpp
>>> diff --git a/main.cpp b/main.cpp
>>> index b95eb4d..35e6d6f 100644
>>> --- a/main.cpp
>>> +++ b/main.cpp
>>> @@ -30,6 +30,66 @@ using code = decltype(
>>> "mov ebx , 1 "
>>> "add eax , ebx "
>>> "mov DWORD PTR [ ebp + 4 ] , eax "
>>> + "mov DWORD PTR [ ebp + 4 ] , eax "
>>> + "mov DWORD PTR [ ebp + 4 ] , eax "
>>> + "mov DWORD PTR [ ebp + 4 ] , eax "
>>> + "mov DWORD PTR [ ebp + 4 ] , eax "
>>> + "mov DWORD PTR [ ebp + 4 ] , eax "
>>> + "mov DWORD PTR [ ebp + 4 ] , eax "
>>> + "mov DWORD PTR [ ebp + 4 ] , eax "
>>> + "mov DWORD PTR [ ebp + 4 ] , eax "
>>> + "mov DWORD PTR [ ebp + 4 ] , eax "
>>> + "mov DWORD PTR [ ebp + 4 ] , eax "
>>> + "mov DWORD PTR [ ebp + 4 ] , eax "
>>> + "mov DWORD PTR [ ebp + 4 ] , eax "
>>> + "mov DWORD PTR [ ebp + 4 ] , eax "
>>> + "mov DWORD PTR [ ebp + 4 ] , eax "
>>> + "mov DWORD PTR [ ebp + 4 ] , eax "
>>> + "mov DWORD PTR [ ebp + 4 ] , eax "
>>> + "mov DWORD PTR [ ebp + 4 ] , eax "
>>> + "mov DWORD PTR [ ebp + 4 ] , eax "
>>> + "mov DWORD PTR [ ebp + 4 ] , eax "
>>> + "mov DWORD PTR [ ebp + 4 ] , eax "
>>> + "mov DWORD PTR [ ebp + 4 ] , eax "
>>> + "mov DWORD PTR [ ebp + 4 ] , eax "
>>> + "mov DWORD PTR [ ebp + 4 ] , eax "
>>> + "mov DWORD PTR [ ebp + 4 ] , eax "
>>> + "mov DWORD PTR [ ebp + 4 ] , eax "
>>> + "mov DWORD PTR [ ebp + 4 ] , eax "
>>> + "mov DWORD PTR [ ebp + 4 ] , eax "
>>> + "mov DWORD PTR [ ebp + 4 ] , eax "
>>> + "mov DWORD PTR [ ebp + 4 ] , eax "
>>> + "mov DWORD PTR [ ebp + 4 ] , eax "
>>> + "mov DWORD PTR [ ebp + 4 ] , eax "
>>> + "mov DWORD PTR [ ebp + 4 ] , eax "
>>> + "mov DWORD PTR [ ebp + 4 ] , eax "
>>> + "mov DWORD PTR [ ebp + 4 ] , eax "
>>> + "mov DWORD PTR [ ebp + 4 ] , eax "
>>> + "mov DWORD PTR [ ebp + 4 ] , eax "
>>> + "mov DWORD PTR [ ebp + 4 ] , eax "
>>> + "mov DWORD PTR [ ebp + 4 ] , eax "
>>> + "mov DWORD PTR [ ebp + 4 ] , eax "
>>> + "mov DWORD PTR [ ebp + 4 ] , eax "
>>> + "mov DWORD PTR [ ebp + 4 ] , eax "
>>> + "mov DWORD PTR [ ebp + 4 ] , eax "
>>> + "mov DWORD PTR [ ebp + 4 ] , eax "
>>> + "mov DWORD PTR [ ebp + 4 ] , eax "
>>> + "mov DWORD PTR [ ebp + 4 ] , eax "
>>> + "mov DWORD PTR [ ebp + 4 ] , eax "
>>> + "mov DWORD PTR [ ebp + 4 ] , eax "
>>> + "mov DWORD PTR [ ebp + 4 ] , eax "
>>> + "mov DWORD PTR [ ebp + 4 ] , eax "
>>> + "mov DWORD PTR [ ebp + 4 ] , eax "
>>> + "mov DWORD PTR [ ebp + 4 ] , eax "
>>> + "mov DWORD PTR [ ebp + 4 ] , eax "
>>> + "mov DWORD PTR [ ebp + 4 ] , eax "
>>> + "mov DWORD PTR [ ebp + 4 ] , eax "
>>> + "mov DWORD PTR [ ebp + 4 ] , eax "
>>> + "mov DWORD PTR [ ebp + 4 ] , eax "
>>> + "mov DWORD PTR [ ebp + 4 ] , eax "
>>> + "mov DWORD PTR [ ebp + 4 ] , eax "
>>> + "mov DWORD PTR [ ebp + 4 ] , eax "
>>> + "mov DWORD PTR [ ebp + 4 ] , eax "
>>> "jmp .loop_label "
>>> ":end_label "
>>> "mov eax , DWORD PTR [ ebp + 16 ] "
>>> @@ -39,4 +99,4 @@ int main()
>>> {
>>> std::cout << "15th element of fibonacci series is: " <<
>>> cai::execute_code<code>;
>>> return 0;
>>> -}
>>> \ No newline at end of file
>>> +}
>>>
>>>
>>>
>>>
>>
>>
>
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