In AT89LP Developer Studio Simulator,under IO.Processor there is CYC_LP entry that shows the elapsed cycles, but there seems to be no way to copy/clear that number.
If you want actual time, it seems you need to manually calculate that using Cycles differences and a Crystal value.

You are probably better to use a more modern Simulator, like TSim51, that shows Cycles (3 fields Total, Sub and Last) and Microseconds, and you can copy/clear any of the 3 fields.