CODEWITHSUNDEEP
c++llvmalias
ashim
ashim

Reputation: 25560

How to make aliases in c++ (on assembly level)?

The question sounds stupid. Surely, just type:

  int i = 1;
  int &k = i;

But after I compile it with llvm ( optimization flag is -O0 ) I have next intermediate interpretation:

  %i = alloca i32, align 4                        ; <i32*> [#uses=2]
  %k = alloca i32*, align 8                       ; <i32**> [#uses=2]

It means that i and k are not aliases (as I understand %k contains address of %i). How to make an example of aliases?

Upvotes: 1

Views: 326

Answers (1)

Oak
Oak

Reputation: 26868

Two pointers are aliased if they point to the same memory location. The concept of aliasing is only applicable for pointers - since a non-pointer value cannot point anywhere. So in your example i can never alias anything.

If you want an aliasing example, look at this snippet:

int i = 1;
int &j = i;
int &k = i;

j and k are aliased.

I'm not exactly sure what you're expecting to see on the LLVM side, especially with -O0. If you were expecting a global alias, those are unrelated and used to provide a second name to an existing global.

Upvotes: 4

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