Updating the getting started guide for Visual Studio users. Specifically, pointing out that you have to pass additional parameters to llvm-lit and explicitly specify python on the command line.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@180869 91177308-0d34-0410-b5e6-96231b3b80d8
Optimize away nop CONCAT_VECTOR nodes.

Optimize CONCAT_VECTOR nodes that merge EXTRACT_SUBVECTOR values that extract from the same vector.

rdar://13402653
PR15866



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@180871 91177308-0d34-0410-b5e6-96231b3b80d8
[inline asm] Return an undef SDValue of the expected value type, rather than
report a fatal error.  This allows us to continue processing the translation
unit.  Test case to come on the clang side because we need an inline asm
diagnostics handler in place.
rdar://13446483

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@180873 91177308-0d34-0410-b5e6-96231b3b80d8
SROA: Generate selects instead of shuffles when blending values because this is the cannonical form.
Shuffles are more difficult to lower and we usually don't touch them, while we do optimize selects more often.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@180875 91177308-0d34-0410-b5e6-96231b3b80d8