llvm dev - Aug 2011 - [LLVMdev] How to place call(s) to functions found in other llvm modules ???

Hi,

I tried this as well, using the following line to add function 
declaration to the caller module.

Function::Create(FT, Function::ExternalLinkage, "gcd", mod);

Where "FT" is the same as before. And the output produced by the 
PrintModulePass becomes:

; ModuleID = 'GCDMain'

declare i32 @gcd(i32, i32)

define i32 @main() {
EntryBlock:
   %tmp = call i32 @gcd(i32 30, i32 50)
   ret i32 %tmp
}

But it still fails to WriteBitcodeToFile, and produces the same error as 
before.

I guess I might be missing some attribute, like "extern" in C ...

Any Comments?

Thanks again for your help,
Hamayun

On 08/31/2011 07:18 PM, Eli Friedman wrote:
> On Wed, Aug 31, 2011 at 10:00 AM, Mian M. Hamayun
> <mian-muhammad.hamayun at imag.fr>  wrote:
>> Hello Everyone,
>>
>> I am trying to create two modules in LLVM, where first module contains
the
>> definition of a function, gcd in this example and another module
contains a
>> call to this function.
>
> You can't reference a global in one module in another module.  Either
> stick with one module, or add a declaration of the function in the
> second module and call that.
>
> -Eli
>

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On Wed, Aug 31, 2011 at 10:54 AM, Mian M. Hamayun
<mian-muhammad.hamayun at imag.fr> wrote:
> Hi,
>
> I tried this as well, using the following line to add function declaration
> to the caller module.
>
> Function::Create(FT, Function::ExternalLinkage, "gcd", mod);
>
> Where "FT" is the same as before. And the output produced by the
> PrintModulePass becomes:
>
> ; ModuleID = 'GCDMain'
>
> declare i32 @gcd(i32, i32)
>
> define i32 @main() {
> EntryBlock:
>  %tmp = call i32 @gcd(i32 30, i32 50)
>  ret i32 %tmp
> }
>
> But it still fails to WriteBitcodeToFile, and produces the same error as
> before.
If you're still getting the "Referencing function in another
module"
error, the call isn't referring to a declaration in the same module.

-Eli

Hi Eli,

Yes, you were right. I was doing something like this ... (which doesn't 
work :()

Function* gcd = inMod.getFunction("gcd");	// Get gcd function from the
input module
...
Function *F_GCD = Function::Create(FT, Function::ExternalLinkage, 
"gcd", mod);	// Add a prototype of the gcd function
...
Value *gcd_val = builder.CreateCall(gcd, args.begin(), args.end(), 
"tmp");		// Add a call to the gcd function.


In fact we don't need to getFunction from the other module.
Just adding a prototype and calling this prototype is sufficient.
Like this ... (this works :))

Function *F_GCD = Function::Create(FT, Function::ExternalLinkage, 
"gcd", mod);	// Add a prototype of the gcd function
...
Value *gcd_val = builder.CreateCall(F_GCD, args.begin(), args.end(), 
"tmp");         // Add a call to the gcd function.


Thanks for you help,
Have a Nice Day !!!
Hamayun

On 08/31/2011 08:11 PM, Eli Friedman wrote:
> On Wed, Aug 31, 2011 at 10:54 AM, Mian M. Hamayun
> <mian-muhammad.hamayun at imag.fr>  wrote:
>> Hi,
>>
>> I tried this as well, using the following line to add function
declaration
>> to the caller module.
>>
>> Function::Create(FT, Function::ExternalLinkage, "gcd", mod);
>>
>> Where "FT" is the same as before. And the output produced by
the
>> PrintModulePass becomes:
>>
>> ; ModuleID = 'GCDMain'
>>
>> declare i32 @gcd(i32, i32)
>>
>> define i32 @main() {
>> EntryBlock:
>>   %tmp = call i32 @gcd(i32 30, i32 50)
>>   ret i32 %tmp
>> }
>>
>> But it still fails to WriteBitcodeToFile, and produces the same error
as
>> before.
>
> If you're still getting the "Referencing function in another
module"
> error, the call isn't referring to a declaration in the same module.
>
> -Eli
>

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