On Fri, May 27, 2011 at 12:14 AM, Richard Henderson <r...@twiddle.net> wrote: > On 05/26/2011 01:25 PM, Blue Swirl wrote: >>> I don't see the point. The C99 implementation defined escape hatch >>> exists for weird cpus. Which we won't be supporting as a QEMU host. >> >> Maybe not, but a compiler with this property could arrive. For >> example, GCC developers could decide that since this weirdness is >> allowed by the standard, it may be implemented as well. > > If you like, you can write a configure test for it. But, honestly, > essentially every place in qemu that uses shifts on signed types > would have to be audited. Really.
OK. > The C99 hook exists to efficiently support targets that don't have > arithmetic shift operations. Honestly. So it would be impossible for a compiler developer to change the logic for shifts for some supported two's-complement logic CPUs (like x86) just because it's legal?
