* Cavium jumps after Marvell's $6 bln offer to buy company
* GM edges up after brokerage upgrade
* Futures up: Dow 4 pts, S&P 0.25 pts, Nasdaq up 5.75 pts (Adds comment, updates prices)
By Sruthi Shankar
Nov 20 (Reuters) - Wall Street indexes were set to open slightly higher on Monday, as a handful of broker recommendations and merger of chipmakers Cavium and Marvell Technology pushed the markets higher in thin pre-Thanksgiving trading.
Shares in Cavium jumped 10 percent in premarket trading after larger rival Marvell said it would buy the company in a deal valued at about $6 billion. Marvell shares also 4.53 percent.
General Motors, up 25 percent for the year but down almost 7 percent in the past month, inched higher after brokerage Guggenheim upgraded the automaker's stock to "buy".
Wal-Mart was down 0.90 percent after Goldman Sachs cut its rating on the stock to "neutral" from "buy". However, fellow Dow member Verizon rose 0.8 percent after Wells Fargo upgraded the wireless carrier's stock to "outperform".
With no major U.S. earnings or economic data scheduled this week, trading volumes were expected to thin ahead of Thursday's holiday and an early close on Friday.
Wall Street had ended last week on a sour note, with major indexes slipping as investors worried about the fate of the Republicans' tax overhaul.
"With earnings season now out of the way, macro news and the prospects of tax reform will basically guide the market," said Peter Cardillo, chief market economist at First Standard Financial in New York.
"I don't expect the market to endure any sharp sell-off or sharp gains (today)."
The U.S. House of Representatives passed their version of a tax bill last week. But the Senate, from which it has already faced resistance, is expected to vote on their version of the bill after Thanksgiving.
Any signs of repositioning ahead of the vote would be liable to impact investors' thinking on the bill.
Bigger movers on Monday included Cardinal Health, down 3.65 percent after Morgan Stanley downgrade, saying the drug distributor's medical segment gave it an outsized exposure to Amazon compared with its peers.
Alibaba also gained 1.23 percent after the e-commerce giant said it would invest $2.87 billion in China's top hypermart operator Sun Art.
At 8:22 a.m. ET (122 GMT), Dow e-minis were up 4 points, or 0.02 percent, with 27,684 contracts changing hands.
S&P 500 e-minis were up 0.25 points, or 0.01 percent, with 190,086 contracts traded.
Nasdaq 100 e-minis were up 5.75 points, or 0.09 percent, on volume of 35,197 contracts. (Reporting by Sruthi Shankar in Bengaluru; Editing by Savio D'Souza)