Messages in this thread | | | Date | Thu, 15 Apr 2010 11:49:56 +0300 | From | Avi Kivity <> | Subject | Re: [PATCH 1/3] X86: Optimise fls(), ffs() and fls64() |
| |
On 04/15/2010 11:48 AM, David Howells wrote: > Avi Kivity<avi@redhat.com> wrote: > > >> Even if Intel processors behave that way, other processors (real and >> emulated) use those manuals as a specification. Emulated processors are >> unlikely to touch an undefined register, but real processors may. >> >> (qemu tcg appears not to touch the output) >> > Possibly because the AMD64 spec specifies that the destination will be > unchanged if the source was 0. >
Likely. But we haven't tested all current and future x86 clones, and they may be based off the Intel documentation instead of the AMD documentation.
-- I have a truly marvellous patch that fixes the bug which this signature is too narrow to contain.
| |