https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90181
--- Comment #11 from Elliott M <ehem+gccbugs at m5p dot com> --- (In reply to Andreas Schwab from comment #1) > x86 doesn't support this either. It just happens to have a few register > classes that consist of a single register, but only because of ISA > constraints. That is a *gross* mischaracterization. Constraint list for x86 includes: 'a', 'b', 'c', 'd', 'S', 'D'. Indeed, that doesn't include bp or sp, but does include *all* the registers which get used for interesting purposes (register-passing calling conventions). Perhaps people writing GCC haven't felt pressure to implement this since they're primarily dealing with x86 and x86 effectively already has this? I'm tempted to propose this to people involved with Clang, then come back here and suggest GCC should copy the feature...
