CODEWITHSUNDEEP
c++x86intelinstruction-setbmi
plasmacel
plasmacel

Reputation: 8538

Compiler macro to detect BMI2 instruction set

I was searching on the web to find a proper solution, without much success. So I hope one of you know something about it: Is there any way to detect the "Intel Bit Manipulation Instruction Sets 2" (BMI2) compile time? I want to make some conditional thing based on the availability of it.

Upvotes: 9

Views: 3350

Answers (2)

RubenLaguna
RubenLaguna

Reputation: 24806

With GCC you can check for the __BMI2__ macro. This macro will be defined if the target supports BMI2 (e.g. -mbmi2,-march=haswell). This is the macro that the instrinsic's headers (x86intrin.h, bmi2intrin.h) uses to check for BMI2 at compile time.

For runtime checks, __builtin_cpu_init() and __builtin_cpu_supports("bmi2") can be used in modern GCC (tested in GCC 5.1, 4.9 and lower doesn't have it).

Upvotes: 10

1201ProgramAlarm
1201ProgramAlarm

Reputation: 32717

Run the CPUID intrinsic function with EAX=7, ECX=0, then check bit 3 of the returned EBX register (the BMI1 flag). EBX bit 8 is the BMI2 flag. Consult your compiler's documentation for how to call CPUID and get the data back from it.

Upvotes: 1

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