Yes, this is a very fair point – it's not like our transcendental function implementations are uniformly correctly rounded anyway – being within 1 ulp is good e

Yes, this is a very fair point – it's not like our transcendental function implementations are uniformly correctly rounded anyway – being within 1 ulp is good enough. I suppose I might be happy if there were a lexical flag for each floating-point instruction (i.e. a bit of the opcode) that chose whether to use the current rounding mode or the normal one. The trouble now is that you have no choice but to use the dynamically scoped one, which is problematic often enough that one is pushed towards just opting out of changing rounding modes altogether.