Nvidia shares ticked higher in midday trading Wednesday, ahead of earnings due after the close. The chip maker's stock has slipped more than 6% from its October all-time high—when it became the first company to reach a $5 trillion market valuation—as investors begin to question whether the AI spending that fuels its growth can be sustained. Despite the semiconductor maker not having missed Wall Street’s targets in at least five years, its earnings have triggered big stock moves in both directions.