maddqpo/msubqpo has a bug handling -0.0 addend when the product exponent is < Emin

open-power-sdk / pveclib

Power Vector Library

Apache License 2.0

29 stars 8 forks source link

Closed munroesj52 closed 1 year ago

munroesj52 commented 1 year ago

When:

IR multiply product is "tiny" (exp < Emin)
and the addend is 0.0
and the signs differ The previous commit would attempt to subtract the product magnitude from 0 generating a signed negative value. The result is a bogus exponent going into normalization and returning an invalid result. The xsmaddqpo unit-test missed this case, but became obvious with the xsmsubqpo unit-test.

The next update will include the fix and updated unit-test.

munroesj52 commented 1 year ago

Pull #176

munroesj52 commented 1 year ago

Closed