[LLVMdev] Simple question

[James Courtier-Dutton]

Hi,

I think this is a very simple question, and it must just be missing something.

I am looking for find out how to assign a constant integer value to
the variable in llvm ir.

The following returns 12, and %var2 = 12.
; ModuleID = 't.c'
target datalayout =
"e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
target triple = "x86_64-pc-linux-gnu"

define i32 @test() nounwind readnone {
  %var1 = xor i32 0, 0
  %var2 = add i32 %var1, 12
  ret i32 %var2
}

Why can't I do?:
; ModuleID = 't.c'
target datalayout =
"e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
target triple = "x86_64-pc-linux-gnu"

define i32 @test() nounwind readnone {
  %var2 = 12
  ret i32 %var2
}

What is the simplest way to make %var2 = 12   ?

Kind Regards

James