The Costs of the Move From 32-Bit to 64-Bit CPUsPermalink

Julio Merino:

All of this growth has been in service of ever-growing programs. But… even if programs are now more sophisticated than they were before, do they all really require access to a 64-bit address space? Has the growth from 8 to 64 bits been a net positive in performance terms?

Let’s try to answer those questions to find some very surprising answers.

We observe massive differences in the machine code generated for the trivial main function. The 64-bit code is definitely smaller than the 32-bit code, contrary to my expectations. But the code is also very different; so different, in fact, that ILP32 vs. LP64 doesn’t explain it.

Was the move to 64-bit CPUs all upside? Julio runs the numbers to show some pros and cons.