On 14 April 2011 16:14, Richard Henderson <r...@twiddle.net> wrote: > On 04/14/2011 02:14 AM, Peter Maydell wrote: >> While we're on the subject of Alpha and flush-to-zero modes, >> do you know what exception bits should get set when Alpha >> flushes a denormal output (not input) to zero? > ... >> I think Alpha should set Inexact and not Underflow, but >> I'm not sure -- can you confirm/deny? > > Deny. > > Page B-8, Add Sub Output Exceptions, > > Exponent underflow and disabled: > Supply +0, no exception delivered to user. > > Exponent underflow and enabled: > Supply +-MIN denorm, Underflow delivered to user. > > Footnote 3, Overflow and Underflow have priority over Inexact.
Thanks. Does "no exception delivered to user" mean also "and do not set FPCR bit UNF" ? The reason I thought it might set Inexact is that I was looking at page 4-79, which says: "If both the UNFD (underflow disable) bit and the UNDZ (underflow to zero) bit are set in the FPCR, the implementation sets the result of an underflow operation to a true zero result. The zeroing of a denormal result by UNDZ must also be treated as an inexact result." -- PMM
