llvm dev - Jul 2010 - [LLVMdev] inline callsites whose function definitions are in different file?

LLVM (2.7 release version) provides 2 implementations for inlining 
function callsites:

- InlineSimple.cpp (-inline):               inline simple callsites 
according to its cost analysis
- InlineAlways.cpp (-always-inline):  inline all callsites that are 
marked with "always_inline" attribute.

They are both subclasses of Inline.cpp that assumes the function's 
definition (body) is in the same Module (file) as its callsites (that 
will be inlined).


I am now having a situation that the functions are defined in file1.c 
(Module1) but all callsites are spread in file2, file3, ...fileN. Would 
LLVM be able to inline such callsites at compile time?

I think the right approach is to conduct inlining at link time (via the 
LTO), but still wonder if it is possible to do it at compile time 
without heavy hacking.


Thank you

Chuck

On Tue, Jul 27, 2010 at 7:46 AM, Chuck Zhao <czhao at eecg.toronto.edu>
wrote:
>  LLVM (2.7 release version) provides 2 implementations for inlining
> function callsites:
>
> - InlineSimple.cpp (-inline):               inline simple callsites
> according to its cost analysis
> - InlineAlways.cpp (-always-inline):  inline all callsites that are
> marked with "always_inline" attribute.
>
> They are both subclasses of Inline.cpp that assumes the function's
> definition (body) is in the same Module (file) as its callsites (that
> will be inlined).
>
>
> I am now having a situation that the functions are defined in file1.c
> (Module1) but all callsites are spread in file2, file3, ...fileN. Would
> LLVM be able to inline such callsites at compile time?
>
> I think the right approach is to conduct inlining at link time (via the
> LTO), but still wonder if it is possible to do it at compile time
> without heavy hacking.
At compiler time while compiling file2.c, how would compile know about
function definition in file1.c  ?
-
Devang

On 7/27/2010 12:40 PM, Devang Patel wrote:
> On Tue, Jul 27, 2010 at 7:46 AM, Chuck Zhao<czhao at
eecg.toronto.edu>  wrote:
>>   LLVM (2.7 release version) provides 2 implementations for inlining
>> function callsites:
>>
>> - InlineSimple.cpp (-inline):               inline simple callsites
>> according to its cost analysis
>> - InlineAlways.cpp (-always-inline):  inline all callsites that are
>> marked with "always_inline" attribute.
>>
>> They are both subclasses of Inline.cpp that assumes the function's
>> definition (body) is in the same Module (file) as its callsites (that
>> will be inlined).
>>
>>
>> I am now having a situation that the functions are defined in file1.c
>> (Module1) but all callsites are spread in file2, file3, ...fileN. Would
>> LLVM be able to inline such callsites at compile time?
>>
>> I think the right approach is to conduct inlining at link time (via the
>> LTO), but still wonder if it is possible to do it at compile time
>> without heavy hacking.
> At compiler time while compiling file2.c, how would compile know about
> function definition in file1.c  ?
> -
> Devang
I don't, and the compiler doesn't neither, that is the problem, unless I
do hacking at compile time.
E.g.:
- put all such function's definitions into file1.c
- force to compile file1.c 1st.
- when compiling file2.c:
   . read file1.bc
   . attach to file2's module
   - do inline analysis + inlining
   - detach the attached file1.bc functions
- repeat for other files.
...

But I don't think this is a good/elegant approach, thus asking the 
LLVM-Dev group.


Thank you

Chuck