Wednesday was a generally good day for the stock market, with major market benchmarks finishing anywhere from roughly unchanged to up half a percent on the day. Positive earnings news from Tuesday night was the initial impetus for early gains, and the Federal Reserve's latest read on monetary policy suggested that interest-rate increases might be slower in coming than some had expected.

Some individual stocks posted much larger gains, and ONEOK Partners (OKS), Advanced Micro Devices (AMD 0.69%), and Arconic (HWM 0.06%) were among the best performers on the day. Below, we'll look more closely at these stocks to tell you why they did so well.

Worker checking on control panel linked to pipeline operations

Image source: ONEOK.

ONEOK Partners unites with its general partner

ONEOK Partners soared 20% after the master limited partnership agreed to a full buyout from its general partner, ONEOK (OKE 0.26%). ONEOK already owned more than 40% of the MLP, but the two entities agreed that ONEOK would acquire the remainder of ONEOK Partners for $9.3 billion in a stock exchange.

As a result of the deal, ONEOK Partners unitholders will receive 0.985 shares of ONEOK stock for every MLP unit they own. ONEOK also said that it intended to increase its dividend following the transaction, and although that won't result in as large a yield as ONEOK Partners paid, it will nevertheless simplify the ownership structure, and also make it easier for the continuing company to raise capital in the public markets in the future.

AMD has investors excited about its future

Advanced Micro Devices jumped 16% in the wake of its fourth-quarter earnings report late Tuesday afternoon. The tech company is still dealing with falling revenue and modest losses, with quarterly sales coming in at $1.11 billion and a net loss of $0.01 per share.

However, AMD sees its revenue declines coming to an end on a year-over-year basis during the current quarter, and CEO Lisa Su was upbeat in saying that new releases in the graphics-chip space and in high-performance computing capabilities should bolster the company's prospects going forward. If AMD can do that while keeping costs in line, as it has promised to do, then today's gains could be just the beginning of a longer-term move upward for the stock.

Arconic gets some interest

Finally, Arconic rose 11%. The value-added spinoff from Alcoa found itself the subject of investor activism on Wednesday, with private equity company Elliott Management writing a letter to fellow shareholders regarding the lightweight-metals specialist.

In a long explanation, Elliott said that it believes Arconic should be worth between $33 and $54 per share even under no-growth assumptions, but it called out CEO Klaus Kleinfeld for what it called an "antiquated" corporate governance structure that has led to underperformance. Kleinfeld defended Arconic's performance in a separate statement, but at this point, Elliott's proxy fight appears likely to continue until the annual shareholder meeting without coming to an early resolution.