Intel® Cilk™ Plus keywords and reducers require the Intel® Cilk™ Plus runtime cilkrts20.dll which can only run on processors that support Intel® Streaming SIMD Extensions 2 (Intel® SSE2).  Using the /arch:IA32 option will build successfully, but the resulting code with those keywords or reducers will crash at runtime on processors that do not support Intel SSE2 with the exception: "0xC000001E: An attempt was made to execute an invalid lock sequence."

Array notations and the #pragma simd extension will build when /arch:IA32 is set, but you will not gain any parallelism from those extensions at that setting.  Elemental functions will give the compile-time error "The 'generic' processor is not supported for vector functions."