GCC's inlining has been a bit brittle, especially when dealing with vector arguments, and also depending on the ABI (4x double vectors without AVX, etc). It's m

GCC's inlining has been a bit brittle, especially when dealing with vector arguments, and also depending on the ABI (4x double vectors without AVX, etc). It's much better in GCC 5.x now. I generally use always_inline for vector arithmetic functions, just to be sure. You never want to have a function call to do just a few SIMD instructions.