在 2022/12/29 上午11:13, Richard Henderson 写道:
On 12/28/22 17:51, gaosong wrote:
A related question though: does the manual mention whether the fpu
instructions only modify the lower 64 bits, or do the high 64-bits
become zeroed, nanboxed, or unspecified?
Only modify the lower 64bits, the high 64-bits is unpecified.
These two options are mutually exclusive. If upper 64 bits
unmodified, then they *are* specified to be the previous contents.
My description is not correct.
'The fpu instruction will modify the low 64 bits, but the high 64 bits
are unspecified and their values are "unpredictable" '.
Thanks.
Song Gao
