[LLVMdev] Eliminating redundant loads

[Hal Finkel]

----- Original Message -----
> From: "Dibyendu Majumdar" <mobile at majumdar.org.uk>
> To: "David Jones" <djones at xtreme-eda.com>
> Cc: "LLVM Developers Mailing List" <llvmdev at cs.uiuc.edu>
> Sent: Sunday, February 22, 2015 4:40:52 PM
> Subject: Re: [LLVMdev] Eliminating redundant loads
> 
> On 22 February 2015 at 20:58, David Jones <djones at xtreme-eda.com>
> wrote:
> > Not sure if this is your problem, but it was mine:
> >
> > You must create (or obtain) a DataLayout *and install it into the
> > Module*.
> >
> > It is possible to generate machine code for IR and not install the
> > DataLayout into the Module. Rather, the DataLayout is used locally
> > at the
> > point where code is generated. However, if you do this, then the
> > alias
> > analyses required to get rid of your redundant loads and stores
> > cannot
> > reason about possible aliasing.
> >
> 
> Hi David,
> 
> I tried setting the module's DataLayout  to the engine's DataLayout.
> Don't see any improvement.
> The memcpy() is to perform a struct assign, so I tried replacing that
> with member by member store.
> But even then the loads are not being eliminated so I guess the
> memcpy() isn't the issue.

If you run the IR through opt -O3 do you get the optimization you expect?

 -Hal

> 
> Regards
> Dibyendu
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-- 
Hal Finkel
Assistant Computational Scientist
Leadership Computing Facility
Argonne National Laboratory