On 2/18/25 4:22 AM, Li, Pan2 wrote:
I see, thanks Richard S for explaining, that makes sense to me and we do
similar things for frm.
It sounds like we need to re-visit what the semantics of vxrm is, from the spec
I only find below words.
Does that indicates callee-save(the spec doesn't mention it but it should if it
is) or something different? Like single-use and then discard.
I may wait a while for the official explanation.
From spec: "The vxrm and vxsat fields of vcsr are not preserved across calls and
their values are unspecified upon entry. "
VXRM isn't a single use or anything like that. We just can't rely on
any incoming value or for it to have any known state after a function
call returns.
It's not heavily used, so getting this wrong can easily slip through the
cracks.
Jeff
