16 ms·

Because your cpu has a base ISA, plus extensions. The compiler doesn't know if you're going to only run this binary on your machine, or distribute it to others

Because your cpu has a base ISA, plus extensions. The compiler doesn't know if you're going to only run this binary on your machine, or distribute it to others that may share your base ISA but possibly not your extensions, so it takes the conservative approach and doesn't use them unless signaled to do so via those compiler flags. Also, I think -march implies -mtune.

AndyKelley 8y ago
In Zig the default target is native, which turns on all the applicable CPU features. If you want to target something other than the native machine you can use --target-os --target-arch parameters. I haven't exposed extra CPU options for cross compiling yet.
- saagarjha 8y ago
  Do you consider the default architecture targetted by GCC (e.g. some old Intel) to be cross compiling? That is, can I make a binary that supports most x86 processors rather than just those with the particular extensions I support, with the current Zig compiler?
  - AndyKelley 8y ago
    Yes. You can pass the native OS and native arch as the cross compilation target, and produce a binary that runs on your machine and others that don't have the same extra CPU features.
- loeg 8y ago
  That explains the difference in the SHA256 code case. Case closed ;-).