The underlying bug was fixed by Marc in July 2019:

2019-07-10  Marc Glisse  <marc.glisse@inria.fr>

	* wide-int.h (wi::lshift): Reject negative values for the fastpath.

and Richard B. agreed to the backport onto the 9 branch.

Bootstrapped/regtested and applied on the 9 branch.


2021-01-06  Eric Botcazou <ebotcazou@adacore.com>

	PR testsuite/90806
	Backport from mainline
	2019-07-10  Marc Glisse  <marc.glisse@inria.fr>

	* wide-int.h (wi::lshift): Reject negative values for the fastpath.

-- 
Eric Botcazou