[LLVMdev] where does %a_addr.0 come from?

[Lang Hames]

Hi Maarten,

If you look at the start of basic block 2 (bb2) you'll see the
following instruction:

 %a_addr.0 = phi i32 [ 1, %bb ], [ 0, %bb1 ]     ; <i32> [#uses=1]

This is an SSA phi node which assigns a value of either 1 or 0 to %a_addr.0
depending on whether control reached the PHI node from basic block bb, or
bb1.

- Lang.

On Thu, Sep 23, 2010 at 11:26 PM, maarten faddegon <
m.faddegon at student.tudelft.nl> wrote:

> Hi,
>
> I am studying SSA and some time ago I asked on this list how to see the
> phi nodes in the llvm ir output. I learned then to use this command:
> opt -mem2reg test.ll -S > test_mem2reg.ll
>
> However, if you look at the output (attached to this message) there is
> something I do not understand. At the end of the function @f at line 18,
> the function returns the variable %a_addr.0. However, this variable is
> never defined or set. The variable %a is. Is "_addr.0"  a way to get the
> address of a variable? I could not find anything about this in in LLVM
> language reference manual.
> Where does this variable come from?
>
>
> thanks,
>   Maarten Faddegon
>
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