> -----Original Message----- > From: Jan Beulich [mailto:[email protected]] > Sent: 26 April 2016 09:28 > To: xen-devel > Cc: Paul Durrant; Wei Liu > Subject: [PATCH] x86/HVM: slightly improve hvm_mmio_{first,last}_byte() > > EFLAGS.DF can be assumed to be usually clear, so unlikely()-annotate > the conditionals accordingly. > > Also prefer latching p->size (used twice) into a local variable, at
Well, it should only be used once since only one of the expressions should be evaluated. > once making it unnecessary for the reader to be sure expressions get > evaluated left to right (operand promotion would yield a different > result if p->addr + p->size - 1 was evaluted right to left). Would that not be cured by replacing 1 with 1ul? Paul > > Signed-off-by: Jan Beulich <[email protected]> > > --- a/xen/include/asm-x86/hvm/io.h > +++ b/xen/include/asm-x86/hvm/io.h > @@ -44,18 +44,18 @@ struct hvm_mmio_ops { > > static inline paddr_t hvm_mmio_first_byte(const ioreq_t *p) > { > - return p->df ? > + return unlikely(p->df) ? > p->addr - (p->count - 1ul) * p->size : > p->addr; > } > > static inline paddr_t hvm_mmio_last_byte(const ioreq_t *p) > { > - unsigned long count = p->count; > + unsigned long size = p->size; > > - return p->df ? > - p->addr + p->size - 1: > - p->addr + (count * p->size) - 1; > + return unlikely(p->df) ? > + p->addr + size - 1: > + p->addr + (p->count * size) - 1; > } > > typedef int (*portio_action_t)( > > _______________________________________________ Xen-devel mailing list [email protected] http://lists.xen.org/xen-devel
