[LLVMdev] Redundant Add Operation in Code Generation?

Ryan Taylor ryta1203 at gmail.com
Fri Oct 19 10:59:57 PDT 2012


  Ok thanks. I was hoping -instcombine might get rid of this obvious
redundancy but it did not. It's not a large deal but inside a loop, which
it is, it could be adding potentially a significant reduction in

On Wed, Oct 17, 2012 at 3:32 PM, Eli Friedman <eli.friedman at gmail.com>wrote:

> On Wed, Oct 17, 2012 at 2:03 PM, Ryan Taylor <ryta1203 at gmail.com> wrote:
> > Eli,
> >
> >   Actually, I stil see this issue without codegenprepare being used. I'm
> > also compiling with -o3.
> >
> >   So I'm still not sure why I'm seeing this issue?
> Hmm... maybe it's LSR doing it?
> Anyway, the general idea is that there are only a few passes which
> perform redundant instruction elimination: GVN, EarlyCSE, and
> InstCombine (IIRC).
> -Eli
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