Floating point is not the problem, it's memory issues mostly due to C defaulting to allowing aliasing. C99 has the `restrict` keyword so you can generally get identical object code from both languages. SSE intrinsics are only available from C, you will either use them or assembly any time you care a lot about performance of tight kernels (very few nontrivial kernels are vectorized adequately by any of today's compilers).
As I recall, this had very little to do with this guy complaints - it was a mixture of C allowing use of x87 80-bit-wide doubles and not allowing sufficient reordering of operations.
That said, yes, restrict was added for this kind of thing.
