On a Solaris 10 Opteron machine, I can let configure guess the target as i386-pc-solaris2.10, and bootstrap works fine. I get a very nice multilib install that can generate x86-64 targets. However, libstdc++ ends up with a poor version of bits/atomicity.h, specifically libstdc++/config/cpu/i386/atomicity.h. That implementation uses a mutex to simulate atomic integers. For performance reasons I need libstdc++ to use the config/cpu/i486/atomicity.h that uses the "lock" mnemonic. If I try to configure with i[456]86-pc-solaris2.10, bootstrap fails when compiling 64 bit targets, and informs me that the CPU I have selected does not support the x86-64 instruction set. If I try to configure with arguments like opteron-pc-solaris2.10, x86-64-pc-solaris2.10, amd64-pc-solaris2.10, etc., these fail to configure at all. Is there configure target that will let libstdc++ choose the better implementation for atomicity.h and also succeed when building the 64 bit targets? Thanks
