[LLVMdev] creating a vreg in eliminateFrameIndex()

[Hal Finkel]

----- Original Message -----
> From: "Steve King" <steve at metrokings.com>
> To: "Hal Finkel" <hfinkel at anl.gov>
> Cc: llvmdev at cs.uiuc.edu, jonathan at codesourcery.com
> Sent: Friday, January 30, 2015 11:20:43 AM
> Subject: Re: [LLVMdev] creating a vreg in eliminateFrameIndex()
> 
> On Fri, Jan 30, 2015 at 8:59 AM, Hal Finkel <hfinkel at anl.gov> wrote:
> >> When the scavenged register is loaded with a simple immediate, is
> >> it
> >> safe to search the BB and replace other uses of the same immediate
> >> with the reg?  In my case this gives a code size reduction.  The
> >> search would stop on finding another use of the scavenged
> >> register.
> >
> > Are you asking whether that would be safe to do on all targets?
> 
> No, just a poor question -- I had in mind only my out-of-tree target.
> I take the answer as "it depends on your target".

Yes, especially not all targets can exchange immediates for registers in a trivial way.

 -Hal

> 

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