ggml-impl : add comment

ggml-ci

Author: ggerganov

ggml-impl.h

@@ -207,6 +207,7 @@ static inline ggml_fp16_t ggml_compute_fp32_to_fp16(float f) {
 #endif // __ARM_NEON
 
 // precomputed f32 table for f16 (256 KB)
+// defined in ggml.c, initialized in ggml_init()
 extern float table_f32_f16[1 << 16];
 
 // On ARM NEON, it's quicker to directly convert x -> x instead of calling into ggml_lookup_fp16_to_fp32,