一切都是LLVM IR中的指针吗？

Question

I iterate through the global vars of the program and am interested for their types.

For a test, like:

#include <stdio.h>

int i=0;
int main(){
    printf("lala %d \n",i);
    return 0;
}

What I get on the output is:

Globals: 
i Type: 14  //14 ==> POINTER TYPE ID !
StackLock: Stack1 
Function Argument: i32* @i

My code:

for (Module::global_iterator I = M.global_begin(), E = M.global_end(); I != E; ++I) {
            std::cout << I->getName().str() << " Type: "<< I->getType()->getTypeID() << std::endl;

            if (I->getType()->isPointerTy() ) {
                std::string o1;
                {
                    raw_string_ostream os1(o1);
                    I->printAsOperand(os1, true);
                }
                char* stackLoc = new char[50];
                sprintf(stackLoc, "Stack%d", StackCounter++);
                errs() << "StackLock: " << stackLoc << "\n";
                errs() << "Function Argument: " << o1 << "\n";
            }

        }

What's the meaning of setting everything as pointers? Is there any way to take the 'real' type? eg on my example: to get the Integer Type for i variable.

Answer 1

According to LLVM IR Reference , Global variables define regions of memory allocated at compilation time instead of run-time, and they must be initialized.

As SSA values, global variables define pointer values that are in scope (ie they dominate) all basic blocks in the program. Global variables always define a pointer to their “content” type because they describe a region of memory, and all memory objects in LLVM are accessed through pointers.

To get the actual type of your global variable, since the global variable's LLVM IR internal type is pointer, the Type::getContainedType(int) or Type::getPointerElementType() could be used to get the pointee type of the pointer, since pointer type is a derived type.