On Mon, Aug 08, 2005 at 04:29:57PM +0300, Omer Zak wrote: > 1. How do you ensure that the compiler did not optimize away the > assignment to q or the call to sqrt() due to recognition that it has no > side-effects (in 80x86 processors, there is a FP sqrt instruction so a > serious compiler knows to inline the function call and that it leaves no > side effects)?
By invoking gcc -S and examining the assembly file. Without optimization, gcc calls sqrt in a loop. With -O3, gcc inlines floating-point instructions to compute sqrt, defaulting to sqrt() in case they somehow go wrong (but apparently here they never do). It still does everything in a loop and stored the result each time in a local variable. I don't know what icc does, I don't have it installed. -- avva "There's nothing simply good, nor ill alone" -- John Donne ================================================================= To unsubscribe, send mail to [EMAIL PROTECTED] with the word "unsubscribe" in the message body, e.g., run the command echo unsubscribe | mail [EMAIL PROTECTED]
