Apple - How do I use llvm-profdata in Mac OS X Yosemite?

You need to use the xcrun tool which will be in your path.

$ xcrun llvm-profdata <args>

The xcrun tool will execute the tool from the currently selected developer tools installation.

If you have Xcode installed you can select which developer tools are used with xcode-select. For example, if you have a beta version installed you can use that version of the command line tools with:

$ sudo xcode-select -s "/Applications/Xcode-beta.app"

and switch back with

$ sudo xcode-select -s "/Applications/Xcode.app"