[MLIR] [LLVM Dialect] Function Pointers

Beginners
#1

Hi all,

I am trying to solve this bug(I am the author of that bug too).

define i32 @foo(i32) {
  ret i32 2
}

define i32 @main() {
  %1 = alloca i32 (i32)*, align 8
  store i32 (i32)* @foo, i32 (i32)** %1, align 8
  %2 = load i32 (i32)*, i32 (i32)** %1, align 8
  %3 = call i32 %2(i32 10)
  ret i32 %3
}

The store instruction fails as it is unable to process the function as a pointer in its operand. What class object is a function pointer going to be (if such a class already exists) and if it does not inherit from Value class, can it?

#2

It isn’t exactly clear if the question pertains to LLVM IR, or the representation of the LLVM dialect in MLIR. Can you clarify?

#3

It isn’t exactly clear if the question pertains to LLVM IR or the representation of the LLVM dialect in MLIR. Can you clarify?

It is about the LLVM IR dialect in MLIR - I wanted a hint on the solution because I am new to tablegen and MLIR.

#4

Sorry for delay. I could not grasp the sense of your question so I investigated the bug instead. The fix is a two-liner so I took the liberty of committing it to avoid wasting your time on it, https://reviews.llvm.org/rGdc553ce646cd.

If I understand the question correctly, the answer is llvm::Function derives from llvm::Constant so you can cast from the latter to the former using dyn_cast and then use mlir::SymbolRefAttr to refer to the function.

#5

Thanks for the clarification @ftynse