[LLVMdev] undefs in phis

[Eli Friedman]

On Thu, Jan 29, 2009 at 2:47 PM, David Greene <dag at cray.com> wrote:
> After phi elimination we have:
>
> bb134:
>  %reg1645 = 1.0
>
> bb74:
>  %reg1176 = MOVAPS %reg1645
>  %reg1177 = MOVAPS %reg1646
> [...]
>
> bb108:
>  %reg1645 = <expr>
>  %reg1646 = %reg1176

I find it a little strange that the IMPLICIT_DEF disappears.  Besides
that, it looks okay up to here.

> Should llvm be able to handle situations like
> this or is the result undefined?

LLVM should be able to handle the IL in question, I think.  Using
undef in the way the given IL is using it is looks legitimate.

-Eli