[llvm] [DXIL][Doc] Update specification of to use TableGen list instead of dag (PR #99055)

[Justin Bogner via llvm-commits]

================
@@ -172,14 +162,55 @@ Shader Model version is represented as follows:
      int Minor = minor;
    }
 
-   // Valid Shader model version records
+
+Concrete representations of valid Shader Model and DXIL versions are defined as follows:
+
+.. code-block::
 
    // Definition of Shader Model 6.0 - 6.8 and DXIL Version 1.0 - 1.8
    foreach i = 0...8 in {
      def SM6_#i : Version<6, i>;
      def DX1_#i : Version<1, i>;
    }
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bogner wrote:

We shouldn't have both Shader Model and DXIL version in here. The point of introducing the DXIL version into the triple was so that we wouldn't need to rely on shader model here, so we should just use DXIL version everywhere here. This also implies that the separate DXILVersion field in DXILOp is unnecessary (what is it used for anyway?) and everywhere that talks about Shader Model should use DXIL version instead.

https://github.com/llvm/llvm-project/pull/99055