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"gcc -O3" breaks rdtsc ??


Hi,

I use a standard sort of macro for invoking the rdtsc instruction from my
C++ code, and it seems wo work fine until I turn on the "-O3" optimization
flag. With this flag enabled, the values returned by this macro seem to be
garbage.

    #define RDTSCLL(_x)          __asm__ __volatile__ ("rdtsc" : "=A" (_x));

My machine:
    Processor: AMD Opteron(tm) Processor 248
    Host type: x86_64-linux
    GCC version: gcc (GCC) 3.4.4 20050721 (Red Hat 3.4.4-2)

Any ideas?

Thanks.

- Tim

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