Hello, Thank you for the reply. So, what you're saying is that the output of `gcc -Q --help=optimizers` doesn't necessarily reflect what optimization gcc is going to do when -O0 is being used, correct? This is because no (or very little) optimization is actually allowed to be done when -O0 is use. Thank you again for the help! David ________________________________ From: Segher Boessenkool <segher@xxxxxxxxxxxxxxxxxxx> Sent: Monday, March 16, 2020 5:34 PM To: Shrader, David Lee Cc: gcc-help@xxxxxxxxxxx Subject: [EXTERNAL] Re: question about knowing when optimization options are used On Mon, Mar 16, 2020 at 11:14:25PM +0000, Shrader, David Lee via Gcc-help wrote: > Most optimizations are only enabled if an -O level is set on the command line. Otherwise they are disabled, even if individual optimization flags are specified. Yes. > The man page says to use `-Q --help=optimizers` to find out what is turned on for the different -O levels as configure-time options can make things different from the defaults shown later in that man page. However, I have found that, even when using -O0, I can turn on optimization options, at least according to the help output: You can enable the *flags*, sure, but with -O0 those flags do not do anything. Exactly as the text above says? The "even if" part. Segher
