gcc 4.2.1 on Niagara (UltraSPARC T1): output uses UltraSPARC3 Extensions?

[Irwin Tillman <irwin@xxxxxxxxxxxxx>]

Platform: gcc 4.2.1 on Solaris 10, on an UltraSPARC T1 (Niagara) system.

When I compile with '-mcpu=niagara', the result is, according to 'file':

   ELF 32-bit MSB executable SPARC32PLUS Version 1, V8+ Required, UltraSPARC3 Extensions Required, dynamically linked

I even get the same result if I instead use '-mcpu=v8'.

I thought the UltraSPARC3 (and even UltraSPARC1) extensions weren't 
supported by UltraSPARC T1 (Niagara) systems.  Am I confused?