On Tue, Jan 17, 2023 at 02:05:22PM +0100, Peter Zijlstra wrote:
> On Wed, Jan 11, 2023 at 03:37:27PM +0300, Kirill A. Shutemov wrote:
>
> > #define __untagged_addr(untag_mask, addr)
> > u64 __addr = (__force u64)(addr); \
> > - s64 sign = (s64)__addr >> 63; \
> > - __addr &= untag_mask | sign; \
> > + if (static_branch_likely(&tagged_addr_key)) { \
> > + s64 sign = (s64)__addr >> 63; \
> > + __addr &= untag_mask | sign; \
> > + } \
> > (__force __typeof__(addr))__addr; \
> > })
> >
> > #define untagged_addr(addr) __untagged_addr(current_untag_mask(), addr)
>
> Is the compiler clever enough to put the memop inside the branch?
Hm. You mean current_untag_mask() inside static_branch_likely()?
But it is preprocessor who does this, not compiler. So, yes, the memop is
inside the branch.
Or I didn't understand your question.
--
Kiryl Shutsemau / Kirill A. Shutemov
