Add support for cases where only some c1+c2 results exceed the max bitshift, clamping accordingly.
Isn't it a little regression for scalar types?
N1.getValueType() == N0.getOperand(1).getValueType()
zeroExtendToMatch(c1, c2, 1 /* Overflow Bit */);
There is no vector analog of zeroExtendToMatch currently, right?
Btw, I don't think I have rights to accept the revision.