[clang] [CIR] Upstream support for switch statements case kinds (PR #138003)

[via cfe-commits]

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@@ -455,7 +456,8 @@ CIRGenFunction::emitCaseDefaultCascade(const T *stmt, mlir::Type condType,
     if (isa<DefaultStmt>(sub) && isa<CaseStmt>(stmt)) {
       subStmtKind = SubStmtKind::Default;
       builder.createYield(loc);
-    } else if (isa<CaseStmt>(sub) && isa<DefaultStmt>(stmt)) {
+    } else if ((isa<CaseStmt>(sub) && isa<DefaultStmt>(stmt)) ||
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Andres-Salamanca wrote:

When we find a cascading case like `case -> case`, we emit a `yield` to indicate a fallthrough.

https://github.com/llvm/llvm-project/pull/138003