The x32 system call ABI [LWN.net]

The x32 system call ABI

Posted Sep 1, 2011 4:24 UTC (Thu) by jzbiciak (guest, #5246)
In reply to: The x32 system call ABI by njs
Parent article: The x32 system call ABI

Further down the page is this note:

    GCC
        The current x32 implementation isn't optimized:
            Atom LEA optimization is disabled.
            Memory addressing should be optimized.

So, that presumably accounts for why 181.mcf slowed down 0.5% to 1% relative to normal 32-bit x86.