Get function implementation for indirect CallInst.

Hi All,
I am using LLVM to analysis some C++ codes. I need to find the related function implementation for a given indirect CallInst.
To make my question a little bit clear, I construct a simple example here. For “ call void %3(%class.Base* %1)”, I need to figure out
Which implementation is called ( it can be manually figured out that _ZN1A5helloEv (A::hello() is called,how to figure it out in a pass ?)

My initial thinking is trace back from "call void %3(%class.Base* %1)” until find %obj1 = alloca %class.A, align 8, but how can I associate %class.A with @_ZTV1A, so I can get the function from @_ZTV1A ?

Thanks!

;virtual tables
@_ZTV1A = linkonce_odr unnamed_addr constant { [3 x i8*] } { [3 x i8*] [i8* null, i8* bitcast ({ i8*, i8*, i8* }* @_ZTI1A to i8*), i8* bitcast (void (%class.A*)* @_ZN1A5helloEv to i8*)] }, align 8
@_ZTV1B = linkonce_odr unnamed_addr constant { [3 x i8*] } { [3 x i8*] [i8* null, i8* bitcast ({ i8*, i8*, i8* }* @_ZTI1B to i8*), i8* bitcast (void (%class.B*)* @_ZN1B5helloEv to i8*)] }, align 8

;A::hello()

define linkonce_odr void @_ZN1A5helloEv(%class.A* %this) unnamed_addr #2 align 2 {
entry:
%this.addr = alloca %class.A*, align 8
store %class.A* %this, %class.A** %this.addr, align 8
%this1 = load %class.A*, %class.A** %this.addr, align 8
%call = call i32 (i8*, …) @printf(i8* getelementptr inbounds ([7 x i8], [7 x i8]* @.str, i32 0, i32 0))
ret void
}

;B::hello()

define linkonce_odr void @_ZN1B5helloEv(%class.B* %this) unnamed_addr #2 align 2 {
entry:
%this.addr = alloca %class.B*, align 8
store %class.B* %this, %class.B** %this.addr, align 8
%this1 = load %class.B*, %class.B** %this.addr, align 8
%call = call i32 (i8*, …) @printf(i8* getelementptr inbounds ([7 x i8], [7 x i8]* @.str.1, i32 0, i32 0))
ret void
}

define i32 @main() #0 {
entry:
%obj1 = alloca %class.A, align 8
%obj2 = alloca %class.B, align 8
%C = alloca %class.Base*, align 8
call void @_ZN1AC1Ev(%class.A* %obj1) #4
call void @_ZN1BC1Ev(%class.B* %obj2) #4
%0 = bitcast %class.A* %obj1 to %class.Base*
store %class.Base* %0, %class.Base** %C, align 8
%1 = load %class.Base*, %class.Base** %C, align 8
%2 = bitcast %class.Base* %1 to void (%class.Base*)***
%vtable = load void (%class.Base*), void (%class.Base*)* %2, align 8
%vfn = getelementptr inbounds void (%class.Base*), void (%class.Base)** %vtable, i64 0
%3 = load void (%class.Base*), void (%class.Base)** %vfn, align 8
call void %3(%class.Base* %1)
ret i32 0
}

Related C++ code

class Base {
public:
virtual void hello();
};

class A: public Base {
public:
void hello() {
printf(“hello\n”);
};
};

class B: public Base {
public:
void hello() {
printf(“world\n”);
};
};

int main() {
A obj1;
B obj2;
Base * C = &obj1;
C->hello();
}

Best Regards,

Chao