Revert revision: 171467. This transformation is incorrect and makes some tests fail. Original message:

Simplified TRUNCATE operation that comes after SETCC. It is possible since SETCC result is 0 or -1.
Added a test.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@171468 91177308-0d34-0410-b5e6-96231b3b80d8
LoopVectorizer:

1. Add code to estimate register pressure.
2. Add code to select the unroll factor based on register pressure.
3. Add bits to TargetTransformInfo to provide the number of registers.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@171469 91177308-0d34-0410-b5e6-96231b3b80d8
Update the docs about the new unroll features.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@171470 91177308-0d34-0410-b5e6-96231b3b80d8
Move the loop vectorizer from O2 to O3. It looks like the increase in code size actually hurts the performance on many programs.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@171471 91177308-0d34-0410-b5e6-96231b3b80d8
Make comment a bit more clear.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@171473 91177308-0d34-0410-b5e6-96231b3b80d8
Add section information for the DWARF5 split debug proposal
string offset section.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@171474 91177308-0d34-0410-b5e6-96231b3b80d8