[DirectX] Disentangle DXIL.td's op types from LLVMType. NFC

LLVMType is both too broad and too narrow for defining DXIL operations, in
different ways. It's too broad in the sense that we don't need the full set of
MVTs - the set of types DXIL operations work on is much smaller. It's too
narrow in the sense that it's difficult to use it for the various fixed
structure types in DXIL, like `%dx.types.Handle` or `%dx.Types.ResRet.f32`.

Replace the usage of LLVMType in DXIL.td with DXILOpParamType, a simple class
that we can define an enum of types from. Further, use this to replace the
"ParameterKind" enum in DXILABI.h that has nothing to do with DXIL's ABI.

Pull Request: llvm#104247

Author: bogner

llvm/docs/DirectX/DXILOpTableGenDesign.rst

@@ -93,18 +93,14 @@ properties are specified as fields of the ``DXILOp`` class as described below.
         class DXILOpClass;
 
    Concrete operation records, such as ``unary`` are defined by inheriting from ``DXILOpClass``.
-6. Return type of the operation is represented as ``LLVMType``.
-7. Operation arguments are represented as a list of ``LLVMType`` with each type
-   corresponding to the argument position. An overload type, if supported by the operation, is
-   denoted as the positional type ``overloadTy`` in the argument or in the result, where
-   ``overloadTy`` is defined to be synonymous to ``llvm_any_ty``.
-
-   .. code-block::
-
-      defvar overloadTy = llvm_any_ty
-
-   Empty list, ``[]`` represents an operation with no arguments.
-
+6. A set of type names are defined that represent return and argument types,
+   which all inherit from ``DXILOpParamType``. These represent simple types
+   like ``int32Ty``, DXIL types like ``dx.types.Handle``, and a special
+   ``overloadTy`` which can be any type allowed by ``Overloads``, described
+   below.
+7. Operation return type is represented as a ``DXILOpParamType``, and arguments
+   are represented as a list of the same. An operation with no return value
+   shall specify ``VoidTy`` as its return.
 8. Valid operation overload types predicated on DXIL version are specified as
    a list of ``Overloads`` records. Representation of ``Overloads``
    class is described in a later section.
@@ -145,10 +141,10 @@ TableGen representations of its properties described above.
      Intrinsic LLVMIntrinsic = ?;
 
      // Result type of the op.
-     LLVMType result;
+     DXILOpParamType result;
 
      // List of argument types of the op. Default to 0 arguments.
-     list<LLVMType> arguments = [];
+     list<DXILOpParamType> arguments = [];
 
      // List of valid overload types predicated by DXIL version
      list<Overloads> overloads;
@@ -233,9 +229,9 @@ overloads predicated on DXIL version as list of records of the following class
 
 .. code-block::
 
-   class Overloads<Version minver, list<LLVMType> ols> {
+   class Overloads<Version minver, list<DXILOpParamType> ols> {
      Version dxil_version = minver;
-     list<LLVMType> overload_types = ols;
+     list<DXILOpParamType> overload_types = ols;
    }
 
 Following is an example specification of valid overload types for ``DXIL1_0`` and

llvm/include/llvm/Support/DXILABI.h

@@ -22,23 +22,6 @@
 namespace llvm {
 namespace dxil {
 
-enum class ParameterKind : uint8_t {
-  Invalid = 0,
-  Void,
-  Half,
-  Float,
-  Double,
-  I1,
-  I8,
-  I16,
-  I32,
-  I64,
-  Overload,
-  CBufferRet,
-  ResourceRet,
-  DXILHandle,
-};
-
 enum class ResourceClass : uint8_t {
   SRV = 0,
   UAV,