Prominent changes to GCC 4.8 include:
- Migrating the compiler's implementation to C++ rather than C.
- A brand new optimization level.
- ARM performance improvements.
- Initial compiler support for Intel Broadwell architecture and the new instruction set extensions it will present next year.
- CPU support for AMD Steamroller and Jaguar.
- Link-time optimization improvements.
- Runtime library improvements, a.k.a. libstdc++.
- ARM 64-bit / AArch64 support.
- Merging of AddressSanitizer and ThreadSanitizer, features previously found in LLVM that were developed by Google.
- Improved C++11 support and initial support for C++1y, the next C++ standard.
- Other new GCC 4.8 features.
The GCC 4.8 release was announced this morning at GNU.org. There's already been some GCC 4.8 compiler benchmarks at Phoronix, but a new round is forthcoming now that the official release is out in the wild.