On 05/08/19 23:13, Richard Henderson 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> > > > r~ >
Queued, thanks. Paolo
