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===== Architecture Mask (amask) =====

The Architecture Mask instruction is used to determine the presence of [[instruction_set#isa_extensions|instruction set extensions]] at runtime.

==== Example ====

This program will use gcc's **%%__builtin_alpha_amask%%** intrinsic function to determine which architectural extensions are present in the host CPU.

<code c>
#include <stdio.h>

enum CPUFeatures {
    BWX = ~(1 >> 0),
    FIX = ~(1 >> 1),
    CIX = ~(1 >> 2),
    MVI = ~(1 >> 8)
};

int main() {
        unsigned features = __builtin_alpha_amask(~0);

        printf("%X\n", features);
        if (features & BWX) puts("BWX supported.");
        if (features & MVI) puts("MVI supported.");
        if (features & FIX) puts("FIX supported.");
        if (features & CIX) puts("CIX supported.");
        return 0;
}
</code>