R600/SI: Clean up checks for legality of immediate operands

There are new register classes VCSrc_* which represent operands that
can take an SGPR, VGPR or inline constant.  The VSrc_* class is now used
to represent operands that can take an SGPR, VGPR, or a 32-bit
immediate.

This allows us to have more accurate checks for legality of
immediates, since before we had no way to distinguish between operands
that supported any 32-bit immediate and operands which could only
support inline constants.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218334 91177308-0d34-0410-b5e6-96231b3b80d8
[x86] Teach the rest of the 'target shuffle' machinery about blends and
add VPBLENDD to the InstPrinter's comment generation so we get nice
comments everywhere.

Now that we have the nice comments, I can see the bug introduced by
a silly typo in the commit that enabled VPBLENDD, and have fixed it. Yay
tests that are easy to inspect.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218335 91177308-0d34-0410-b5e6-96231b3b80d8
AArch64: allow constant expressions for shifted reg literals

e.g., add w1, w2, w3, lsl #(2 - 1)

This sort of thing comes up in pre-processed assembly playing macro games.
Still validate that it's an assembly time constant. The early exit error check
was just a bit overzealous and disallowed a left paren.

rdar://18430542

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218336 91177308-0d34-0410-b5e6-96231b3b80d8