[LLVMdev] Problem in X86 backend (again)

Akira Hatanaka ahatanak at gmail.com
Wed Oct 29 09:49:32 PDT 2014

I was just pointing out that "reg" is defined by two instructions, which
shouldn't happen when the code is still in SSA.

"reg" is first defined by phi,
// Update phi node
BuildMI(*MBB_erase, MBB_erase->end(), db, TII->get(X86::PHI),

and defined again by this instruction:

BuildMI(*MBB_erase, MBB_erase->end(), db, TII->get(X86::ADD64ri32),

On Wed, Oct 29, 2014 at 3:07 AM, Rinaldini Julien <
julien.rinaldini at heig-vd.ch> wrote:

> >> // Increment loop variable and jmp
> >> BuildMI(*MBB_erase, MBB_erase->end(), db, >>
> TII->get(X86::ADD64ri32),reg).addReg(reg).addImm(8);
> >
> > It looks like this instruction is defining virtual register "reg" the
> second time.
> Thx for your answer...
> Why would it define it again? I just want to use this register and add
> something to it...
> Cheers
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