[clang] [HLSL][Matrix] introduce MatrixElementExpr as accessor and swizzle operator (PR #171225)

[Farzon Lotfi via cfe-commits]

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@@ -4472,6 +4543,59 @@ void ExtVectorElementExpr::getEncodedElementAccess(
   }
 }
 
+void MatrixElementExpr::getEncodedElementAccess(
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farzonl wrote:

done see `ForEachMatrixAccessorIndex`. I may have gotten a little overzealous and tried to also abstract the HLSL specific parsing parts to  `GetHLSLMatrixAccessorFormat` But I don't knoiw how useful that is is because we can't access LangOpts in an Expr. Still like the formating in a seperate helper because it keeps things cleaner so left it that way.

https://github.com/llvm/llvm-project/pull/171225