[llvm-dev] Understanding AllocaInst

[David Greene via llvm-dev]

David Blaikie via llvm-dev <llvm-dev at lists.llvm.org> writes:

> The type of an alloca is a pointer to the type of the allocated object. For
> instance:
>
> This C++ source code:
>
>   int i;
>   float f;
>   f1(i, f);
>
> compiles to this LLVM IR:
>
>  %i = alloca i32, align 4
>   %f = alloca float, align 4
>   %0 = load i32, i32* %i, align 4
>   %1 = load float, float* %f, align 4
>   call void @_Z2f1if(i32 %0, float %1)
>
> So you can see the type of an alloca of i32 is i32* and the type of an
> alloca of float is float*.


And the type of an alloca of i32* is i32** which is where that comes
from.  So Avery is doing an alloca of an i32*, a pointer rather than an
integer.

HTH,

                 -David