------- Comment #7 from jakub at gcc dot gnu dot org 2010-05-27 11:44 ------- You are wrong. It is user's responsibility to choose correct constraints for the inline assembly, the compiler doesn't try to understand what the inline assembly is doing or even check its semantics, all it does is perform replacements in it (replacing %0, %1, %2 in this case). Not every constraint is suitable for every use in the assembly obviously, otherwise we wouldn't need multiple constraints. The "g" constraint allows a register, immediate or memory, all must be valid in the instruction and it is up to the compiler which one it chooses. "g" constraint is usable say for mov eax, %2; which can work well with registers, immediates or memory. But as you use [%2] instead, memory isn't valid, all that is valid is either a register or register + immediate or register + X*register2 + immediate (the usual i?86 addressing modes).
-- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44288
