-march=<name of native> doesn't seem to set flags -march=native does?

[Roger Pack]

Hello.
As a note after a discussion [1]

I ran into this oddness:


$ gcc-6 -march=native -Q --help=target | grep march
  -march=                     		ivybridge
$ gcc-6 -march=native -Q --help=target | grep sse3
  -msse3                      		[enabled]
  -mssse3                     		[enabled]
$ gcc-6 -march=ivybridge -Q --help=target | grep sse3
  -msse3                      		[disabled]
  -mssse3                     		[disabled]

It appears that specifying (in this case) "-march=ivybridge" which is
the native, isn't enough/the same as specifying -march=native?
In addition, the "cache sizes" don't seem to be called out with
"-march=ivybridge" as they are with "-march=native"
Anybody know what I'm missing here?
Thank you!
-roger

[1] http://stackoverflow.com/a/24213278/32453