[llvm-dev] How to insert instructions before each function calls?

[Ryan Taylor via llvm-dev]

Mehdi,

 Sorry, I misread his original post.

 So something like:

 XXXInsrtInfo   *XII;    // target instruction info
  MachineBasicBlock::iterator MI = MachineBasicBlock(YourCallInst);
 MachineBasicBlock *MBB = YourCallInst->getParent(); // basic block
location of your call inst
 BuildMI(*MBB, MI, DebugLoc(), XII->get(XXX:::INSTRUCTION)......);

The BuildMI params are going to depend on what you want to do with the
instruction being inserted.
 http://llvm.org/docs/doxygen/html/MachineInstrBuilder_8h.html

-Ryan



On Sun, Sep 4, 2016 at 1:45 AM, Mehdi Amini <mehdi.amini at apple.com> wrote:

>
> On Sep 3, 2016, at 6:18 PM, Ryan Taylor via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
> So one way might look like this:
>
> IRBuilder<> Builder(&*BB); // BB = Function::iterator OR IRBuilder<>
> Builder(CallInst->getParent());
> Builder.SetInsertPoint(CallInst);
> InstructionClass *YourNewInstruction = builder.CreateInstructionClass(.....);
> // InstructionClass = type of instruction you are inserting
>
>
> I’m not sure how the IRBuilder would work at the MI level, as Shucai was
> asking.
>
>
>
>
> On Sat, Sep 3, 2016 at 6:04 PM, Ryan Taylor <ryta1203 at gmail.com> wrote:
>
>> Take a look at IRBuilder and SetInsertPoint().
>>
>> On Sep 3, 2016 18:02, "SHUCAI YAO via llvm-dev" <llvm-dev at lists.llvm.org>
>> wrote:
>>
>>> I'm trying to insert some instructions before each function calls
>>> (before arguments push):
>>>    lea %EAX, label                      ----- new instructions
>>>    mov [ESP+stacksize], %EAX  ----- new instructions
>>>    push arg1
>>>    push arg2
>>>    ...
>>>    push argn
>>>    call callee_name
>>>
>>> I am a newbie to LLVM. I tried to use buildMI() to insert the
>>> instructions in the lowercall() function. But I couldn't put these
>>> instructions in the right positions. Is there a way to locate the position
>>> by using MachineBasicBlock iterator?
>>>
>>
> Can you describe more precisely what are you trying to achieve?
> I.e. what are these instructions? Why do you want to do that? It may lead
> to a different answer.
>
> —
> Mehdi
>
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