On Mon, Mar 13, 2017 at 11:27:32AM +0100, Florian Weimer wrote: > On 03/13/2017 05:34 AM, Andreas Dilger wrote: > >Not that it is a huge deal either way, but I'd think it is harder for the > >compiler to optimize across a function call boundary like memset() vs. a > >struct initialization in the same function where it can see that all but > >a few of the fields are being overwritten immediately before they are used. > > GCC treats memset as a function call only if options such as > -ffreestanding or -fno-builtin are enabled, or if memset is > redefined in a header file. Does the kernel do this? > No, it does not. So gcc treats memset() as a request to clear memory, not as a request to call a function called "memset()" specifically. On x86_64 it's compiling it into a "rep stos" instruction. - Eric
