synchthread inside the Warp

Accelerated Computing CUDA CUDA Programming and Performance
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How did you syncthreads within the same warp?

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Threads within the same warp are automatically sync by hardware at branch merge points.
I doubt programmer can do any syncthreads within the same warp.
The above code still might not syncthreads within the same warp, especially while branches are present.

kernel()
{
…
branch diverge
…
if (tid < 32) {do something}
…
branch reconverge
…
}