Debug Info: code clean up.

Remove unnecessary creation of LexicalScope in collectDeadVariables.
The created LexicialScope was only used to get isAbstractScope, which
should be false from the creation:
"new LexicalScope(NULL, DIDescriptor(SP), NULL, false);".

We can also remove a DenseMap that holds the created LexicalScopes.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@193196 91177308-0d34-0410-b5e6-96231b3b80d8
R600/SI: Don't assert on SCC usage

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@193198 91177308-0d34-0410-b5e6-96231b3b80d8
[X86][FastISel] Add a comment to help understanding changes made in r192636.

<rdar://problem/15192473>


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@193199 91177308-0d34-0410-b5e6-96231b3b80d8