CODEWITHSUNDEEP
c++compiler-constructionllvmllvm-ir
nico
nico

Reputation: 1406

In LLVM, what "type" is a bitcast of a function inside a call? How to access this function?

In my llvm IR code, I have the following line:

%tmp = call i32 @decf1(void (i8*)* bitcast (void (%a_type*)* @decf2 to void (i8*)*), i8 %x3, i8* @external_type)

I am trying to extract a_type and decf2 programmatically, but I seem not to get access to them.

bool runOnFunction(Function &F) override {
errs() << "Initializing Test pass\n";

for (BasicBlock &BB : F) {
  for (Instruction &I : BB) {
    // New Instruction
    errs() << "\n\n"
           << "=====================\n"
           << "- - - - - - - - - - -\n"
           << "NewInstruction:\n";
    I.dump();
    errs() << "\n";

    // New Operands
    errs() << "- - - - - - - - - - -\n"
           << "Operands:\n";
    for (Use &U : I.operands()) {
      errs() << "Type: ";
      U->getType()->print(errs());
      errs() << "\n";
      errs() << "Name: " << U->getName() << "\n";
    }
    errs() << "\n";
}

This pass produces me the following output for the instruction containing the cast.

=====================
- - - - - - - - - - -
NewInstruction:
  %tmp = call i32 @decf1(void (i8*)* bitcast (void (%a_type*)* @decf2 to void (i8*)*), i8 %x3, i8* @external_type)

- - - - - - - - - - -
Operands:
Type: void (i8*)*
Name:
Is Instruction: No
Is Function: No

Type: i8
Name: x3
Is Instruction: Yes
          %x3 = mul i8 %x2, %x2
Is Function: No

Type: i8*
Name: external_type
Is Instruction: No
Is Function: No

Type: i32 (void (i8*)*, i8, i8*)*
Name: decf1
Is Instruction: No
Is Function: Yes
        Is Declaration: Yes

It seems that the first printed operand has to do with the bitcast. How can I get the bitcast and the operands/type/function it is casting?

Upvotes: 1

Views: 1387

Answers (1)

nico
nico

Reputation: 1406

It seems that Value::stripPointerCasts() is a way to get the the cast decf2 function as a Function *.

Still need to elaborate on how to get the a_type from there.

Upvotes: 2

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