I noticed from the end-of-beta survey that optionprotect-parens was introduced, presumably to comply with that part of C and C++ standards while permitting optimization of sum reduction when /fp:fast is set (as it is by default in ICL).
protect-parens shows excellent results in my testing of C and Cilk(tm) Plus code, with performance gains up to 40%, even though several cases of pessimization in violation of parens had already been corrected (where previously /fp:source was needed to optimize).
It kills simd optimization of several cases of C++ accumulate() and inner_product(). Was that expected?
I suppose it's credible that protect-parens makes /fp:fast consistent with Microsoft compiler for STL, but I hate to revive the old argument that STL is incompatible with simd optimization or the mis-used terminology "code modernization."