[asan] add -asan-coverage=3: instrument all blocks and critical edges. 

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@217098 91177308-0d34-0410-b5e6-96231b3b80d8
[x86] Teach the asm comment printing to only print the clarification of
an immediate operand when we don't have instruction-specific comments.

This ensures that instruction-specific comments are attached to the same
line as the instruction which is important for using them to write
readable and maintainable tests. My next commit will just such a test.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@217099 91177308-0d34-0410-b5e6-96231b3b80d8
[x86] Teach the new vector shuffle lowering about the simplest of
'insertps' patterns.

This replaces two shuffles with a single insertps in very common cases.
My next patch will extend this to leverage the zeroing capabilities of
insertps which will allow it to be used in a much wider set of cases.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@217100 91177308-0d34-0410-b5e6-96231b3b80d8