[LLVMdev] Wrong behavior modifying and executing llvm::Function with JIT Engine

[Yaron Keren]

getFunction() -> getPointerToFunction()




2014-06-29 6:40 GMT+03:00 Yaron Keren <yaron.keren at gmail.com>:

> Hi Adrian,
>
> freeMachineCodeForFunction is required but recompileAndLinkFunction is
> not,
> you can use getFunction() always.
>
> Try to  M->dump() calling M->getFunction() where M is the Module *.
> See if how the changes appear in the module dump as expected.
>
> Yaron
>
>
>
>
>
> 2014-06-29 5:56 GMT+03:00 Adrian Ortega <elfus0.1 at gmail.com>:
>
>>  Hello,
>>
>> The problem I'm having is that I modify a function body by using
>> 'Value::replaceAllUsesWith' and then execute it with the JIT engine several
>> times but I always get the output from the first iteration for all the
>> iterations.
>>
>> This is what I do:
>>
>>
>> I generate the following 2 functions on the fly based on the FunctionType
>> of the declaration below in C code.
>>
>>
>> define i32 @get_int_5(i32, i32) #1 {
>>   ret i32 5
>> }
>>
>> define i32 @get_int_10(i32, i32) #1 {
>>   ret i32 10
>> }
>>
>> I have the following C code:
>>
>>
>> // This is only a declaration
>> // I use this FunctionType to generate the functions above
>> int sum(int a, int b);
>>
>> int get_int()
>> {
>>     return sum(a,b);
>> }
>>
>>  I replace the  call to 'sum()' by calling Value::replaceAllUsesWith for
>> one of the functions generated above, run with JIT. I checked the code
>> generated and it actually changes the call from 'sum()' to 'get_int_5()'
>> and I get a 5 as return value when I call the function with the JIT
>> execution engine.
>>
>> Then I repeat the previous step using 'Value::replaceAllUsesWith' for the
>> next function I generated and run it with JIT. Then again the code
>> generated is what I expected, this time
>> function call changes from 'sum()' to 'get_int_10()', however the problem
>> is I get a 5 instead of a 10.
>>
>> I tried 'recompileAndLinkFunction' as well as
>> 'freeMachineCodeForFunction' and I always get the return value from the
>> first function, and not the second as I should even though the generated
>> code that I dump() says that it has the correct function call.
>>
>> I am using version 3.4 for both clang and llvm. And also I'm using the
>> JIT Engine and not the MCJIT.
>>
>> Do you have have any idea why the references or 'uses' changes are not
>> reflected in the code JIT'ed ?
>>
>> Regards.
>>
>>
>>
>>
>>
>>
>>
>>
>> _______________________________________________
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>>
>>
>
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