[LLVMdev] getTripCount requires which optimization passes?

[ether zhhb]

hi,

On Fri, May 7, 2010 at 8:59 AM, Trevor Harmon <Trevor.W.Harmon at nasa.gov>wrote:

> Hi,
>
> For me, getTripCount always returns null, even for trivial loops such
> as:
>
> void simple(int j) {
>     for (int i = 0; i < 10; i++) {
>         j++;
>     }
> }
>
> Looking through the mailing list archive, it appears that getTripCount
> requires certain optimization passes to run first, but it's not clear
> which ones. There doesn't seem to be any documentation on this. Does
> anybody know exactly which passes must run in order for getTripCount
> to work?
>
As the comment said:
  /// The IndVarSimplify pass transforms loops to have a form that this
  /// function easily understands.

you could try -indvars.

>
> Thanks,
>
> Trevor
>
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best regards
ether
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