Document minimum GCC version for -fopenmp-simd
@@ -178,7 +178,8 @@ equivalent is), you should enable OpenMP 4 SIMD support by defining
enabling OpenMP support in your compiler. GCC and ICC both support a
flag to enable only OpenMP SIMD support instead of full OpenMP (the OpenMP
SIMD support doesn't require the OpenMP run-time library); for GCC the
-flag is `-fopenmp-simd`, for ICC `-qopenmp-simd`. SIMDe also supports
+flag is `-fopenmp-simd` (requires GCC version 4.9 or later), for ICC
+the flag is `-qopenmp-simd`. SIMDe also supports
using [Cilk Plus](https://www.cilkplus.org/), [GCC loop-specific
pragmas](https://gcc.gnu.org/onlinedocs/gcc/Loop-Specific-Pragmas.html),
or [clang pragma loop hint
