On Mon, Jun 07, 2021 at 01:31:24PM -0700, Linus Torvalds wrote: > > Is it useful in general for the kernel to have separate "read" and > > "write" clobbers in asm expressions? And for other applications? > > See above. It's actually not all that uncommon that you have a "this > doesn't modify memory, but you can't move writes around it". It's > usually very much about cache handling or memory ordering operations, > and that bit test example was probably a bad example exactly because > it made it look like it's about some controlled range. > > The "write memory barroer" is likely the best and simplest example, > but it's in not the only one. Thanks for the examples! I opened <https://gcc.gnu.org/PR100953> so that we can easily track it. Segher
