[LLVMdev] Use of movupd instead of movapd for x86

[Sebastien DELDON-GNB]

OK, 

I found a work-around by adding ,align 8 to vector load/store.
Thanks all for your answers


> -----Original Message-----
> From: Evan Cheng [mailto:evan.cheng at apple.com]
> Sent: Tuesday, March 01, 2011 7:26 AM
> To: Sebastien DELDON-GNB
> Cc: David A. Greene; llvmdev at cs.uiuc.edu
> Subject: Re: [LLVMdev] Use of movupd instead of movapd for x86
> 
> 
> On Feb 28, 2011, at 2:58 AM, Sebastien DELDON-GNB wrote:
> 
> > Understood for the aligned case, I want to measure performance
> degradation for unaligned case.
> > I mean unaligned case versus aligned. I know this is stupid, but I
> want to try to pass a <4 x float>* as parameter of a routine and at the
> call site I want to pass a misaligned pointer. Since LLVM is generating
> movapd instruction it will raise an exception (SEGFAULT), I just want
> to know if there is a way to enforce
> > generation of movupd instruction instead of movapd.
> 
> If llvm is generating movapd then it believes the pointer is aligned.
> Without having more information it's impossible to tell what the issue
> is.
> 
> Evan
> 
> >
> > Seb
> >
> >> -----Original Message-----
> >> From: David A. Greene [mailto:greened at obbligato.org]
> >> Sent: Friday, February 25, 2011 5:13 PM
> >> To: Sebastien DELDON-GNB
> >> Cc: llvmdev at cs.uiuc.edu
> >> Subject: Re: [LLVMdev] Use of movupd instead of movapd for x86
> >>
> >> Sebastien DELDON-GNB <sebastien.deldon at st.com> writes:
> >>
> >>> Hi all,
> >>>
> >>> Is there a way to force llc to generate movupd instruction instead
> of
> >> movapd for x86 target ?
> >>>
> >>> I know that movapd is more performant, but I would like to measure
> >> degradation when alignment constraints are not met.
> >>
> >> On modern processors a movupd on aligned data is going to be
> >> indistinguishable in performance from a movapd.
> >>
> >>                               -Dave
> >
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