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Global Variables in LLVM IR

Global functions can be constants and called from anywhere in the program in LLVM IR. First, we must create their identifier, starting with the symbol @, followed by their name.

@my_global

Then we must indicate its visibility, if it is accessible from outside, for use with the linker, or proprietary; in any case, we use the keywords private or global accordingly.

@my_global private

Then we can indicate if it is a constant (it cannot be mutated), or if we do not put anything, it is mutable. For constants, we use the keyword;constant excuse the redundancy.

@my_global private constant

Now we must indicate its type.

@my_global private constant [12 x i8]

Now we must indicate its value.

@my_global private constant [12 x i8] c"hello world\00"

We can specify its memory alignment, but if the value is different from 1, it is ignored by any LLVM/Clang tool when compiling.

@my_global private constant [12 x i8] c"hello world\00", align 1