[clang] [mlir] [OpenACC] Implement tile/collapse lowering (PR #138576)

[Andy Kaylor via cfe-commits]

================
@@ -336,6 +348,52 @@ class OpenACCClauseCIREmitter final
       return clauseNotImplemented(clause);
     }
   }
+
+  void VisitCollapseClause(const OpenACCCollapseClause &clause) {
+    if constexpr (isOneOfTypes<OpTy, mlir::acc::LoopOp>) {
+      llvm::APInt value =
+          clause.getIntExpr()->EvaluateKnownConstInt(cgf.cgm.getASTContext());
+
+      if (value.getBitWidth() != 64)
+        value = value.sext(64);
----------------
andykaylor wrote:

Is it possible for value to be wider than 64 bits?

https://github.com/llvm/llvm-project/pull/138576