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

[hameeza ahmed via llvm-dev]

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.

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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