[LLVMdev] Generating New Functions

[John Criswell]

On 10/14/13 5:53 AM, Abhinash Jain wrote:
> How can I generate a new function at compile time and insert some instruction
> onto it, through llvm pass.
> eg.
>
> 1)  %y = alloca i32, align 4
> 2)  %z = alloca i32, align 4
> 3)  %t = alloca i32, align 4
> 4)  %2 = load i32* %y, align 4
> 5)  %3 = load i32* %z, align 4
> 6)  %add = add nsw i32 %2, %3
> 7)  %4 = load i32* %t, align 4
> 8)  %add1 = add nsw i32 %add, %4
> 9)  store i32 %add1, i32* %x, align 4
>
> whenever I see a store instruction, I want to generate a new function and
> insert/copy all instruction (from 1 to 9) on that generated function.

You should consult the doxygen documentation on llvm::Function to 
determine how to create new functions.  For most LLVM objects, there is 
either a new method or a static Create/create method that will create 
the objects.  The doxygen docs contain the list of methods for each 
class and will usually have the information for which you're looking:

http://llvm.org/doxygen/classllvm_1_1Function.html

As for copying instructions into a new function, look at the functions 
in lib/Transforms/Utils/CloneFunction.cpp (note that the pathname of the 
file may have moved; this is its location in LLVM 3.2).

-- John T.

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