At least for C and C++, why don’t GCC/clang implement constant time primitives as intrinsics? It would be useful in the meantime to developers working on crypto

At least for C and C++, why don’t GCC/clang implement constant time primitives as intrinsics? It would be useful in the meantime to developers working on cryptographic code, would provide better guarantees, and could emit useful errors when compiling against platforms where such guarantees cannot be provided. It would also act as prior art for standardization. I’ve always thought it was strange that assembly wasn’t used for some of these primitives, since you don’t control the codegen, but letting the compiler provide intrinsics would solve the problem without requiring every project to write their own assembly routines.