"gcc -v" output should include default values corresponding to the -march and -mtune options.
As a reference: http://gcc.gnu.org/ml/gcc-help/2008-07/msg00062.html -- Summary: "gcc -v" should include default arch/tune values Product: gcc Version: 4.3.1 Status: UNCONFIRMED Severity: enhancement Priority: P3 Component: driver AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: vincent at vinc17 dot org http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36731