hack around bug in emscripten

src/libcore/mem.rs

@@ -503,7 +503,9 @@ pub fn swap<T>(x: &mut T, y: &mut T) {
         // that swapping either 32 bytes or 64 bytes at a time is most efficient for intel
         // Haswell E processors. LLVM is more able to optimize if we give a struct a
         // #[repr(simd)], even if we don't actually use this struct directly.
-        #[repr(simd)]
+        //
+        // FIXME repr(simd) broken on emscripten
+        #[cfg_attr(not(target_os = "emscripten"), repr(simd))]
         struct Block(u64, u64, u64, u64);
         struct UnalignedBlock(u64, u64, u64, u64);