Optimized integer vector multiplication operation by replacing it with shift/xor/sub when it is possible. Fixed a bug in SDIV, where the const operand is not a splat constant vector.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@184931 91177308-0d34-0410-b5e6-96231b3b80d8
Suppress llvm/test/Other/can-execute.txt on msys bash.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@184932 91177308-0d34-0410-b5e6-96231b3b80d8