Add a basic-block autovectorization pass.

This is the initial checkin of the basic-block autovectorization pass along with some supporting vectorization infrastructure.
Special thanks to everyone who helped review this code over the last several months (especially Tobias Grosser).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@149468 91177308-0d34-0410-b5e6-96231b3b80d8

tools/opt/opt.cpp

@@ -480,6 +480,7 @@ int main(int argc, char **argv) {
   PassRegistry &Registry = *PassRegistry::getPassRegistry();
   initializeCore(Registry);
   initializeScalarOpts(Registry);
+  initializeVectorization(Registry);
   initializeIPO(Registry);
   initializeAnalysis(Registry);
   initializeIPA(Registry);