Analyst upgrades: GSF, RIG, FTO, TSO and AUDC

MOST NOTEWORTHY: GlobalSantaFe Corp, Transocean, Frontier Oil, Tesoro and Audio Codes were today's noteworthy upgrades:

JP Morgan upgraded shares of GlobalSantaFe Corporation (NYSE: GSF) and Transocean Inc (NYSE: RIG) to Neutral from Underweight based on valuation and improving deepwater rig fundamentals.
Frontier Oil Corporation (NYSE: FTO) was upgraded at Banc of America to Buy from Neutral as they believe the company's assets are ideally located to access cheap Canadian oil sands production. They feel the stock should trade closer to its replacement value, which they estimate at $55/share.
The firm also raised Tesora Corporation (NYSE: TSO) to Buy from Neutral, as the firm believes Terero is the best play on the extended refining cycle given its exposure to California.
CIBC upgraded shares of AudioCodes (NASDAQ: AUDC) to Sector Outperformer from Sector Performer on valuation after their checks suggested the company's business is stabilizing and cost cutting is tracking ahead of plan, which could bring upside EPS estimates.

OTHER UPGRADES:

GSI Commerce (NASDAQ: GSIC) was upgraded to Buy from Hold at Jefferies.
Apache Corporation (NYSE: APA) was upgraded to Buy from Neutral at Goldman Sachs.
Amgen Inc (NASDAQ: AMGN) was upgraded to Buy from Neutral at Merrill Lynch.
BB&T Capital upgraded shares of Skechers USA (NYSE: SKX) to Buy from Hold.
Bernstein upgraded shares of Cognizant Technology (NASDAQ: CTSH) to Outperform from Market Perform.