[LLVMdev] Use of movupd instead of movapd for x86

[Sebastien DELDON-GNB]

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.

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