Salesforce CEO Marc Benioff. Robert Galbraith/Reuters Salesforce has spent over $4 billion on acquisitions in the past year alone, and it's making some investors grow concerned about the company's spending strategy.

According to a note by Macquarie Research on Tuesday, Salesforce may have some explaining to do during its earnings call on Wednesday to ease the investors worried about the company's record-high buying spree over the past year.

It writes:

"Salesforce's recent M&A activity has inspired a wave of speculation in the press about who Salesforce may acquire next, making many investors uneasy about the company's direction despite particularly little substantial news from the company.

"We are therefore looking for Salesforce to provide clarification on its M&A strategy during its upcoming conference call, which we believe would reassure investors about management's M&A discipline."

Salesforce has bought about a dozen companies in the past 12 months, the fastest pace in the company's history. That includes the $2.8 billion Demandware acquisition, which was the largest deal Salesforce has made to date, and the $750 million deal for the 40-person startup Quip.

On top of that, Salesforce CEO Marc Benioff is reported to have tried to outbid Microsoft's $26 billion offer for LinkedIn at one point, causing investors to question the company's M&A strategy.

Other research firms like UBS and Wedbush raised the same concerns, saying that investors are worried that Salesforce could be finding its organic growth slowing and looking to pursue expensive deals even if they are dilutive to earnings. That's also partly pressuring Salesforce's share price, which has remained roughly flat after announcing its Demandware acquisition in June.

Still, Piper Jaffray noted that most of the acquisitions make sense because they've been in the artificial-intelligence and machine-learning space, in which Salesforce is launching its new product, Einstein. Salesforce is expected to keep up its growth because of the strong potential in its service and marketing cloud products, which is also helping the company attract "some of the best talent in the industry," the note said.

It added:

"While investors we have spoken with are getting incrementally more cautious around the pace of Salesforce's M&A machine, we believe that acquisitions such as BeyondCore, which are tuck-in in nature, can expand the scope of existing solutions to make them more impactful and successful in the marketplace."

Perhaps we'll find out more on Wednesday when Salesforce reports its quarterly earnings.

Here's what analysts are expecting, according to Yahoo Finance: