https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69176
--- Comment #9 from Wilco <wdijkstr at arm dot com> --- (In reply to Andrew Pinski from comment #8) > (In reply to Wilco from comment #7) > > > > I think the problem is the constraints on *add<mode>3_pluslong allows > > > > all immediates. > > > > > > I'm not sure what you mean here - there are 4 constraints that should all > > > be > > > true before the instruction is matched: GPI, aarch64_pluslong_immediate, > > > 'i' > > > and "!aarch64_plus_operand (operands[2], VOIDmode) && !aarch64_move_imm > > > (INTVAL (operands[2]), <MODE>mode)". > > > > It appears reload creates the instruction without doing the last check - > > this is incorrect as it might be an instruction that is disabled (eg. not > > supported by the selected architecture)... > > > > However a trivial workaround is to always expand the pattern by changing the > > "&& true" into "true". I'll post a patch. > > plus patterns are special to reload (this is documented IIRC). So I think > there should be only one plus pattern for DI mode. I see, that would explain why it doesn't check the condition. Merging into a single instruction should be possible. That still wouldn't check the condition of course, so we'd need to split anything that isn't a single add (given this odd reload case is so rare, it's not an issue). There is also a secondary issue in that the large number of reloads in the example generate quite inefficient code. With a few tweaks I got a 5% reduction in instruction count.
