SLPVectorizer: Add support for vectorizing trees that start at compare instructions.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179504 91177308-0d34-0410-b5e6-96231b3b80d8
Rename the slp-vectorizer clang/llvm flags. No functionality change.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179505 91177308-0d34-0410-b5e6-96231b3b80d8
Add an option -vectorize-slp-aggressive for running the BB vectorizer. Make -fslp-vectorize run the slp-vectorizer.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179508 91177308-0d34-0410-b5e6-96231b3b80d8
Docs: merge the description of the BB and SLP vectorizers and document the -fslp-vectorize-aggressive flag.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179510 91177308-0d34-0410-b5e6-96231b3b80d8
Document our desire to enable the loop vectorizer on -Os in future releases.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179511 91177308-0d34-0410-b5e6-96231b3b80d8
Recommit r179497 after fixing uninitialized variable.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179512 91177308-0d34-0410-b5e6-96231b3b80d8
Revert "Recommit r179497 after fixing uninitialized variable." until
I can fix the testcases here:

http://lab.llvm.org:8011/builders/clang-native-arm-cortex-a9/builds/6952

This reverts commit r179512 due to testcases specifying triples
that they didn't actually mean and causing failures on other platforms.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179513 91177308-0d34-0410-b5e6-96231b3b80d8