Update predictions for test cases.

In D81076#2095354, @shawnl wrote:

What about shr and ashl?

a = b << 64;
or
a = b >> 64;

In D82145#2110583, @lkail wrote:

Better keep original RUN lines and adding new RUN with opt added and check prefix named like CHECK-DIV-REM-PAIRS.

In D82145#2110509, @lkail wrote:

It looks not an NFC patch to me, the test predicates are changed

CHECK: modsw -> CHECK-NOT: modsw

I'm curious if it is unchanged that opt is added to RUN lines while the OperationAction keeps Custom. If so, adding opt to RUN lines can be an NFC patch, and making OperationAction Legal can be another FC patch.

In D81076#2095354, @shawnl wrote:

What about shr and ashl?

a = b << 64;
or
a = b >> 64;

Add RUN lines for pwr8.

Add assertions.

Change the diff base from master to D81073.

Use std::iota and std::rotate to simplify vector rotation.

Fix whitespace error.