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

[Ryan Taylor via llvm-dev]

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

-Ryan




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?
>>
>> Any suggestions are appreciated.
>>
>> Thanks!
>> Shucai
>>
>>
>>
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>> llvm-dev at lists.llvm.org
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>>
>>
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