Apple Power Mac G5 - Manual (Page 22)

New Compiler
Apple has also supplied a new compiler, GCC version 3.3, that generates optimal code
for the Power Mac G5. The new compiler produces code that executes efficiently on
G5, G4, and G3 systems, so a single Mac OS X application runs optimally on each
of Apple’s supported processor architectures, allowing developers to build and qualify
a single version of their applications for both 32-bit and 64-bit Mac systems. In fact,
Mac OS X Panther itself was completely recompiled using the GCC 3.3 compiler to
achieve the best possible performance from the PowerPC G5.
22 Technology and
Performance Overview
Power Mac G5