[TableGen] Allow shift operators to take bits<n>

Convert the operand to int if possible, i.e. if the value is properly
initialized.  (I suppose there is further room for improvement here to also
peform the shift if the uninitialized bits are shifted out.)

With this little change we can now compute the scaling factor for compressed
displacement with pure tablegen code in the X86 backend.  This is useful
because both the X86-disassembler-specific part of tablegen and the assembler
need this and TD is the natural sharing place.

The patch also adds the missing documentation for the shift and add operator.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@213277 91177308-0d34-0410-b5e6-96231b3b80d8
[X86] AVX512: Move compressed displacement logic to TD

This does not actually move the logic yet but reimplements it in the Tablegen
language.  Then asserts that the new implementation results in the same value.

The next patch will remove the assert and the temporary use of the TSFlags and
remove the C++ implementation.

The formula requires a limited form of the logical left and right operators.
I implemented these with the bit-extract/insert operator (i.e. blah{bits}).

No functional change.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@213278 91177308-0d34-0410-b5e6-96231b3b80d8
[X86] AVX512: Use the TD version of CD8_Scale in the assembler

Passes the computed scaling factor in TSFlags rather than the old attributes.

Also removes the C++ version of computing the scaling factor (MemObjSize)
along with the asserts added by the previous patch.

No functional change.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@213279 91177308-0d34-0410-b5e6-96231b3b80d8
[X86] AVX512: Rename EVEX_CD8V to CD8_Form

This is to match the naming of CD8_EltSize, CD8_Scale, etc.

No functional change.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@213280 91177308-0d34-0410-b5e6-96231b3b80d8
[X86] AVX512: Add disassembler support for compressed displacement

There are two parts here.  First is to modify tablegen to adjust the encoding
type ENCODING_RM with the scaling factor.

The second is to use the new encoding types to compute the correct
displacement in the decoder.

Fixes <rdar://problem/17608489>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@213281 91177308-0d34-0410-b5e6-96231b3b80d8