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
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