Improve code generation for nearbyhint under -ffast-math

Fix #548

Author: serge-sans-paille

include/xsimd/arch/common/xsimd_common_math.hpp

@@ -1904,8 +1904,9 @@ namespace xsimd
                 // to v. That's not what we want, so prevent compiler optimization here.
                 // FIXME: it may be better to emit a memory barrier here (?).
 #ifdef __FAST_MATH__
-                volatile batch_type d0 = v + t2n;
-                batch_type d = *(batch_type*)(void*)(&d0) - t2n;
+                batch_type d0 = v + t2n;
+                asm volatile("" ::"r"(&d0) : "memory");
+                batch_type d = d0 - t2n;
 #else
                 batch_type d0 = v + t2n;
                 batch_type d = d0 - t2n;