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Re: [RFC] [autovect patch] Implement vectorization hints


On Thu, 24 Feb 2005 16:27:39 -0800, Devang Patel <dpatel@apple.com> wrote:
> 
> This patch implements two #pragmas that developers can use to give
> hints to auto vectorization pass. These pragmas are inserted in the
> source file before the loop. They are effective only on the very next
> loop in the source file.
> 
> "#pragma novector" instructs compiler to not vectorize the loop.
> Programmer may decide to do so for various reasons.
> 
> "#pragma ivdep" instructs compiler to ignore possible data dependence
> when data dependence analyzer is not able determine it. This is useful
> in a situation where compiler does not have enough information to prove
> data independence, but developer knows about it.
 
Where should I place the #pragma ivdep if I have a nested loop?

#pragma ivdep 
  for (;;)
    for (;;)
       ;

or
  for (;;)
#pragma ivdep
    for (;;)
       ;

or even before both loops?

Thanks,
Richard.


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