pragma clang fp already exists which enables fast math flags within a scope. It currently supports pragma clang fp contract(value) and pragma clang fp reassociate(on).

I would like this extended to cover other fast math flags, in particular arcp. For something like

float fast_div(float x, float y) { #pragma clang fp reciprocal(on) return x / y; } 

I would hope to get

float @fast_div(float %, float %y) { %0 = fdiv arcp float %x, %y ret float %0 }