On Wed, 27 Mar 2019 14:00:47 -0400, Sasha Levin wrote: > From: Jiong Wang <jiong.wang@xxxxxxxxxxxxx> > > [ Upstream commit db0a4b3b6b83a081a9ec309cc8178e5c9b4706a5 ] > > Shifts by zero do nothing, and should be treated as nops. > > Even though compiler is not supposed to generate such instructions and > manual written assembly is unlikely to have them, but they are legal > instructions and have defined behavior. > > This patch correct existing shifts code-gen to make sure they do nothing > when shift amount is zero except when the instruction is ALU32 for which > high bits need to be cleared. > > For shift amount bigger than type size, already, NFP JIT back-end errors > out for immediate shift and only low 5 bits will be taken into account for > indirect shift which is the same as x86. > > Reviewed-by: Jakub Kicinski <jakub.kicinski@xxxxxxxxxxxxx> > Signed-off-by: Jiong Wang <jiong.wang@xxxxxxxxxxxxx> > Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx> > Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> Nope.
