glibc-2.11 fails to compile without the bit_AVX #define that is included in gcc-4.4.2 (or later i presume)
Steps to Reproduce:
Many files fail to compile with undefined reference to bit_AVX
Can you attach the build.log of the compilation failure and your emerge --info plz?
sys-libs/glibc-2.11 builds fine with sys-devel/gcc-4.4.1