* config/i386/i386.opt (mcx16, msahf): New options.
        * config/i386/i386.c (x86_cmpxchg16b, x86_sahf): Remove.
        (ix86_tune_features) [X86_TUNE_USE_SAHF]: Enable for m_GENERIC.

        * config/i386/driver-i386.c (bit_LAHF_LM): New define.
        (host_detect_local_cpu): Detect cx16 and lahf_lm cpuid bits.
        Output -mcx16 and -msahf options when corresponding bit is set.

        * doc/invoke.texi (i386 and x86-64 Options): Document -mcx16
        and -msahf options.

testsuite/ChangeLog

        * testsuite/gcc.target/i386/cmpxchg16b-1.c: New test.

From-SVN: r122884