U.S. stocks ended lower Wednesday, with losses in Advanced Micro Devices, Palantir and other technology companies, as investors worried about pricey valuations and whether Wall Street's AI rally has reached its peak.

Alphabet fell ahead of its quarterly results after the bell, which will give investors a fresh glimpse of how much the Google-owner's massive investments in AI are contributing to its top-line sales growth.

Advanced Micro Devices tumbled after the chipmaker forecast quarterly revenue that disappointed investors and suggested it is having a tough time competing against AI heavyweight Nvidia.

Nvidia dropped and the PHLX semiconductor index ended sharply lower.

Palantir slumped, reversing sharp gains from the previous day that were driven by the AI data company's strong quarterly sales.

"The size of the infrastructure buildout is unprecedented, and the pace of consumers and businesses adopting AI tools is also unprecedented," said Jed Ellerbroek, a portfolio manager at Argent Capital in St. Louis.

"The stock market is having a really hard knowing where to price the stocks and what the future looks like," Ellerbroek continued. "The market is suddenly skeptical and concerned about it."

Some software companies added to recent losses amid worries that rapidly advancing AI could disrupt industry incumbents. Snowflake and Datadog both fell.

"If you've got legacy software that's old and clunky, you're a ripe target for AI. We're a bit bearish on software in general, with the whole impetus of AI," said Josh Chastant, portfolio manager, public investments at GuideStone Funds.

Investors selling AI-related stocks shifted into less pricey companies that sat out the tech rally in recent years. The S&P 500 value index gained for a fifth straight session, while the S&P 500 growth index dropped.

According to preliminary data, the S&P 500 lost 35.59 points, or 0.51%, to end at 6,882.22 points, while the Nasdaq Composite lost 350.61 points, or 1.51%, to 22,903.13. The Dow Jones Industrial Average rose 246.56 points, or 0.51%, to 49,487.55.

Super Micro Computer's shares jumped after the company raised its annual revenue forecast on sustained demand for its AI-optimized servers as companies ramp up data-center capacity.

Limiting losses in the S&P 500, shares of the drugmaker Eli Lilly rallied after the company forecast 2026 profit above Wall Street expectations.

The government's closely watched jobs report for January has been pushed back from its scheduled release on Friday due to a four-day partial government shutdown that ended on Tuesday.

In the meantime, the ADP national employment report on Wednesday showed that U.S. private payrolls increased less than expected in January amid job losses in the professional and business services as well as manufacturing sectors.