[clang] [CIR] Implement builtin MatrixExtract operation (PR #229879)

[Erich Keane via cfe-commits]

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@@ -235,6 +235,7 @@ struct MissingFeatures {
   static bool emitLValueAlignmentAssumption() { return false; }
   static bool emitNullCheckForDeleteCalls() { return false; }
   static bool emitNullabilityCheck() { return false; }
+  static bool emitIndexAssumption() { return false; }
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erichkeane wrote:

emitMatrixIndexAssumption? 

https://github.com/llvm/llvm-project/pull/229879