https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65436
--- Comment #7 from David <gccbugzilla at limegreensocks dot com> --- While I don't yet see a case here to justify making this change generally, it may be useful to change this for private builds of gcc. For those cases, change this line in gcc/genconfig.c: max_recog_operands = 29; /* We will add 1 later. */ This generates MAX_RECOG_OPERANDS in insn-config.h, which controls the number of parameters for asm statements. Like Andrew, I would be interested to see what you are doing that modifies > 15 registers in inline asm on x86. My gut says there's got to be a cleaner way than throwing more parameters at it, but maybe not.