Avoiding denormal values in C++

Question

After searching a long time for a performance bug, I read about denormal floating point values.

Apparently denormalized floating-point values can be a major performa

Answer 1

To have (flush-to-zero) FTZ (assuming underflow is masked by default) in gcc:

#define CSR_FLUSH_TO_ZERO         (1 << 15)
unsigned csr = __builtin_ia32_stmxcsr();
csr |= CSR_FLUSH_TO_ZERO;
__builtin_ia32_ldmxcsr(csr);

In case it's not obvious from the names, __builtin_ia32_stmxcsr and __builtin_ia32_ldmxcsr are available only if you're targeting a x86 processor. ARM, Sparc, MIPS, etc. will each need separate platform-specific code with this approach.