[LLVMdev] Simple question

[Óscar Fuentes]

James Courtier-Dutton <james.dutton at gmail.com> writes:

> 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   ?

To add to the other response, it is important to note that your %var1,
%var2 above are not variables at all, because they can't be reassigned
(i.e. they can't appear again on the left hand of a %varX = ...
expression.) They are just names for the values corresponding to the
instructions.