From some "High-Performance Computing" book; "It is hard to eradicate from C++'ers the need for objects, classes, etc. ..."
"For high-performance computing you want to avoid such software engineering abstractions as classes, objects, etc...."
Therefore, I would say, since Haskell makes possible many fine-levels of abstraction, if the compiler can strip most of these away, then it would come close to the speed of C (i.e. C++ without most of the software engineering abstractions).
Still, I remember that quote that, "Another level of indirection solves everything."
If you're Penn & Teller, "Another level of misdirection solves everything."