On Mon, 5 Aug 2019 at 22:13, Richard Henderson <r...@twiddle.net> wrote: > > On 8/5/19 11:03 AM, Peter Maydell wrote: > > The x86 architecture requires that all conversions from floating > > point to integer which raise the 'invalid' exception (infinities of > > both signs, NaN, and all values which don't fit in the destination > > integer) return what the x86 spec calls the "indefinite integer > > value", which is 0x8000_0000 for 32-bits or 0x8000_0000_0000_0000 for > > 64-bits. The softfloat functions return the more usual behaviour of > > positive overflows returning the maximum value that fits in the > > destination integer format and negative overflows returning the > > minimum value that fits. > > > > Wrap the softfloat functions in x86-specific versions which > > detect the 'invalid' condition and return the indefinite integer. > > > > Note that we don't use these wrappers for the 3DNow! pf2id and pf2iw > > instructions, which do return the minimum value that fits in > > an int32 if the input float is a large negative number. > > > > Fixes: https://bugs.launchpad.net/qemu/+bug/1815423 > > Signed-off-by: Peter Maydell <peter.mayd...@linaro.org> > > --- > > I've tested that this fixes the LP:1815423 test case. If anybody > > has an x86 VM image to hand that has node.js installed it would > > also be useful to test the operations in > > https://bugs.launchpad.net/qemu/+bug/1832281 > > (I don't have such a VM.) > > > > The other approach here would be to make the softfloat functions be > > flexible enough to allow this behaviour -- from my reading of IEEE754 > > I think the exact returned result for 'invalid' inputs for float to > > int conversions is not specified. > > > > target/i386/ops_sse.h | 88 +++++++++++++++++++++++++++++-------------- > > 1 file changed, 60 insertions(+), 28 deletions(-) > > I guess this is exactly what we already do in fpu_helper.c. > Reviewed-by: Richard Henderson <richard.hender...@linaro.org>
Huh, so we do; I didn't notice that :-) thanks -- PMM
