I couldn't find anything on the matter, but what happens if -march is repeated more than once? I would assume the usual behavior that the last flag "wins".
On a haswell host, the following: gcc -march=native -march=opteron or gcc -march=opteron -march=native both emit code which is illegal for the opteron ISA, as if -march=native had special treatment. Specifying -march=opteron alone works as intended. Since I generally override the default flags in makefiles by appending exceptions where needed, I'd sort of expected the regular behavior. Is this intended? If not, should I try to generate a small test case? Thanks.
