[llvm-dev] LLVM IR linking separate function definitions in header files in single IR

[Mehdi AMINI via llvm-dev]

On Sun, Feb 10, 2019 at 8:21 AM hameeza ahmed <hahmed2305 at gmail.com> wrote:

> Hello,
> If we have @_Znwm(i64 32) this,
> It means allocation of 32 bytes on heap right?
>

Yes, that's right. If you look at the link I posted earlier to the source
code, the argument is passed directly to malloc.

-- 
Mehdi



>
> Thank You
>
> On Sun, Jan 6, 2019 at 10:15 PM Mehdi AMINI <joker.eph at gmail.com> wrote:
>
>>
>>
>> On Sun, Jan 6, 2019 at 3:36 AM hameeza ahmed <hahmed2305 at gmail.com>
>> wrote:
>>
>>> Thank You..
>>> I am observing memory allocation instructions malloc and new operator in
>>> LLVM IR.
>>> In my considered benchmark memory is allocated using new operator as
>>> follows.
>>> *return static_cast<_Tp*>(::operator new(__n * sizeof(_Tp)));*
>>>
>>> How can I observe such allocations in IR? I mean which instruction in IR
>>> is equivalent to above code i.e new operator.
>>>
>>
>> I think I answered in my previous email: "The line you are posting above
>> is present multiple times, for example in the
>> function _ZN9__gnu_cxx13new_allocatorINSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEEE8allocateEmPKv"
>> and: "Calls to @_Znwm are allocating memory."
>>
>> Did you search for these calls in the IR? Can you clarify what else you
>> need?
>>
>> --
>> Mehdi
>>
>>
>>
>>>
>>> Please help
>>> Thank You
>>>
>>> On Sun, Jan 6, 2019 at 4:32 AM Mehdi AMINI <joker.eph at gmail.com> wrote:
>>>
>>>>
>>>>
>>>> On Sat, Jan 5, 2019 at 3:08 PM hameeza ahmed <hahmed2305 at gmail.com>
>>>> wrote:
>>>>
>>>>> Thank You...
>>>>> My issue is i m observing malloc instructions in LLVM IR.. When I
>>>>> compiled certain benchmark codes i.e graphbig. They consume memory but when
>>>>> I see IR there is no malloc..
>>>>>
>>>>
>>>> This is confusing, you first wrote that you are "observing malloc
>>>> instructions in LLVM IR" but then you wrote "when I see IR there is no
>>>> malloc".
>>>>
>>>>
>>>>
>>>>> By observing in detail i came to know following line which exist in
>>>>> header file new_allocator.h is taking memory;
>>>>> *return static_cast<_Tp*>(::operator new(__n * sizeof(_Tp)));*
>>>>>
>>>>
>>>> Your original question was "I want to have a single IR with all the
>>>> definitions of the called functions that are implemented in header files".
>>>>
>>>> The IR you're sending contains all the code defined in the header. The
>>>> line you are posting above is present multiple times, for example in the
>>>> function _ZN9__gnu_cxx13new_allocatorINSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEEE8allocateEmPKv
>>>>
>>>>
>>>>
>>>>> but in IR there is no malloc...
>>>>>
>>>>
>>>> Do you have calls to malloc in the source code?
>>>>
>>>>
>>>>> how can i identify such instructions in IR...by call void @_ZN??
>>>>> My IR is attached here..
>>>>>
>>>>
>>>> Calls to @_Znwm are allocating memory. They are not implemented in a
>>>> header:
>>>> https://code.woboq.org/gcc/libstdc++-v3/libsupc++/new_op.cc.html#50
>>>> (see the call to malloc there).
>>>>
>>>> In general, calls to malloc can likely be caught at runtime: run in a
>>>> debugger and break into malloc.
>>>>
>>>> best,
>>>>
>>>> --
>>>> Mehdi
>>>>
>>>>
>>>>
>>>>
>>>>>
>>>>> Please help.
>>>>>
>>>>> On Fri, Jan 4, 2019 at 4:21 AM Mehdi AMINI <joker.eph at gmail.com>
>>>>> wrote:
>>>>>
>>>>>>
>>>>>>
>>>>>> On Tue, Jan 1, 2019 at 1:41 PM hameeza ahmed via llvm-dev <
>>>>>> llvm-dev at lists.llvm.org> wrote:
>>>>>>
>>>>>>> Hello,
>>>>>>> I have different codes with separate files with functions
>>>>>>> implemented. I want to view all function definitions/ instructions in
>>>>>>> single IR. I am able to do this by llvm-link for codes which have
>>>>>>> definition implemented in .c files...
>>>>>>> But there are some codes which have definitions instructions in
>>>>>>> header files. These functions are called from .c file. I want to have a
>>>>>>> single IR with all the definitions of the called functions that are
>>>>>>> implemented in header files..
>>>>>>>
>>>>>>> How to do this?
>>>>>>> Please help...
>>>>>>>
>>>>>>
>>>>>> I assume that your  "function defined in a header"  are marked as
>>>>>> inline? There is no semantic concept of "header" in C/C++: moving code from
>>>>>> a .c to a .h (or renaming a file) does not change anything to what the
>>>>>> compiler will do with it.
>>>>>>
>>>>>> Depending on the language (GNU-C89, C99 vs C++, see here:
>>>>>> https://en.wikipedia.org/wiki/Inline_function ), the semantic of
>>>>>> inline functions is different.
>>>>>> If you can provide an minimal example it would be easier.
>>>>>>
>>>>>> Best,
>>>>>>
>>>>>> --
>>>>>> Mehdi
>>>>>>
>>>>>>
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