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

[Yaron Keren]

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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