On Mon, 23 Sep 2024, Bradley Lucier via Gcc-help wrote: > So it appears that the Xeon X5460 CPU from 2008 doesn't have the rdtscp > instruction, which is used by default by this version of gcc on x86-64 when no > architecture is specified. GCC doesn't emit neither the rdtsc nor rdtscp instruction on its own, it can appear only if the source code is using the corresponding built-in or instrinsic; and GCC doesn't "promote" rdtsc to rdtscp depending on -march. So if you see rdtscp in binary there must be rdtscp in source code. Can you investigate the source corresponding to the problematic code in the binary? > If I say > > gcc -Q --help=target > > I get > > -march= x86-64 > > > with a lot of other options enabled or disabled. > > So, is there a way to tell what the default -march= value for a given version > of gcc is? -Q --help=target gives that value. Alexander
