[clang] [HLSL][Matrix] Make matrix truncation respect default matrix memory layout (PR #184280)

[Deric C. via cfe-commits]

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@@ -4457,6 +4457,29 @@ class ConstantMatrixType final : public MatrixType {
     return Column * NumRows + Row;
   }
 
+  /// Given a row-major flattened index \p Index, return the corresponding
+  /// {row, column} position.
+  std::pair<unsigned, unsigned> getRowMajorRowAndColumn(unsigned Index) const {
+    return {Index / NumColumns, Index % NumColumns};
+  }
+
+  /// Given a column-major flattened index \p Index, return the corresponding
+  /// {row, column} position.
+  std::pair<unsigned, unsigned>
+  getColumnMajorRowAndColumn(unsigned Index) const {
+    return {Index % NumRows, Index / NumRows};
+  }
+
+  /// Given a flattened index \p Index, return the corresponding {row, column}
+  /// position. If \p IsRowMajor is true, interprets \p Index as a row-major
+  /// flattened index. Otherwise, interprets it as a column-major flattened
+  /// index.
+  std::pair<unsigned, unsigned> getRowAndColumn(unsigned Index,
+                                                bool IsRowMajor = false) const {
+    return IsRowMajor ? getRowMajorRowAndColumn(Index)
+                      : getColumnMajorRowAndColumn(Index);
+  }
+
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Icohedron wrote:

Could be useful in the future, but yea I can just reintroduce these when they are actually needed.

https://github.com/llvm/llvm-project/pull/184280