Mihail Platonov <dofg@xxxxx> writes: > what is the semantics of "r" specifier in subx operand (%r2)? > and what is the meaning of connection between this specifier and "J" > constraint? > __asm__ __volatile__ ( > ... > "subx %r2,%3,%%g1\n\t" > : "=&r" ((USItype)(r1)), > "=&r" ((USItype)(r0)) > : "%rJ" ((USItype)(x3)), > "rI" ((USItype)(y3)), > ... The 'r' constraint means that that operand must be a general register. The 'J' constraint means that it must be the integer zero. Using both rJ and together means that the operand must be either a general register or the integer zero. The '%' means that the operands are commutative, which seems to me to be extremely unlikely for a sub instruction. Unless this is used in some very strange way, that almost has to be a bug. Ian
