Firefox has x86, x86-64, and ARM as tier-1 architectures. It has a whole bunch of tier-2 architectures that are supported but to a lesser extent (e.g. a patch

Firefox has x86, x86-64, and ARM as tier-1 architectures. It has a whole bunch of tier-2 architectures that are supported but to a lesser extent (e.g. a patch that breaks one of them doesn't automatically get backed out immediately). People are shipping and using Firefox on various of those architectures, including JS jits on at least Sparc and PPC.