[SelectionDAG] computeKnownBits - early-out if any BUILD_VECTOR element has no known bits

No need to check the remaining elements - no common known bits are available.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@285399 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed