> > > Or something equivalent. Example: How do you know moving an > > > expression out of a for loop is valid? The optimizer needs to > > > understand the control flow. > > > > is this still a useful thing to be doing? > > Yes.
what's your argument? my argument is that the cpu is so fast relative to the network and disk, that wasting a few cycles is a good tradeoff for compiler and debugging simplicity, and compile speed. further, i'm not sure the compiler is in a position to know when strength reduction will make sense. intel, for example, does a lot of optimization that is "not architectural". that's code that means they won't tell you what will be a net win. i can think of a number of things that might defeat moving code out of a loop, such as the computation using otherwise idle functional units, keeping the value in the trace cache, keeping the value out of l2, the loop detector, etc. - erik
