如何在c ++中创建别名（在汇编级别）？

Question

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?

Answer 1

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.