Julian Seward wrote:
Recently I've been playing with CVS qemu-system (softmmu) on amd64
and had some stability problems. I decided to run Valgrind's amd64
instruction-set tests (derived from qemu's) to see if they picked up
anything. Resulting diffs are attached.
There are a bunch of differences for the C flag for rotates
(rol/ror) by multiples of the word size. I don't think these
are significant, but who knows.
This is a bug in QEMU. From the manuals, the C flag must be updated even
if the resulting shift is zero. I just modified the QEMU tests to catch
this problem (it is not x86_64 specific).
Perhaps more worryingly are the 20 or so lines at the bottom
of the diff. These I believe are for double-to-int/short
conversions for a value which is out of range for an int/short;
the hardware produces 0x80000000/0x8000 respectively, which is
the "integer indefinite"; QEMU produces zero. I can imagine some
obscure routine somewhere checking for integer indefinite after
conversion and being confused as a result.
I guess the problem comes from the usage of lrintl() on x86_64 in
fpu/softfloat-native.c, but I cannot test it yet.
Fabrice.
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