The heavy volume in XLNX today shows arbitrage interest with increasing confidence that the AMD acquisition will be approved soon. Some are looking to buy and hold AMD on the cheap. Others are just interested in the one-time boost. The latter group will want to sell for a quick profit as soon as the approval is announced. That will put pressure for XLNX to go down.
However, that sell pressure will be matched or exceeded by two types of big-money institutional buyers: 1) arbitrage specialists looking to make bank on a sure-thing, even if it is only for a small percentage gain; and 2) funds looking to acquire or increase a large stake in AMD, taking advantage of the massive churn to buy and hold massive quantities of shares without pushing the price up too much too fast.
At the same time, AMD shorts may have to cover as fast as possible to avoid even greater losses. Day trading specialists will move in-and-out over the course of a few days to try to benefit from the volatility. Some long-term XLNX holders may also choose to take their profits and move on to other opportunities.
When the dust settles, a lot more AMD shares will be in the firm hands of smart-money institutional buyers. Any catalyst after that--such as the announcement of new Exynos 2200 chips--should send the SP sharply higher. I'm planning on just patiently waiting through the volatility. Whatever happens, AMD is a keeper for many quarters to come.

$Xilinx(XLNX)$ $AMD(AMD)$