[clang] Implement CIR switch case simplify with appropriate tests (PR #140649)

[Bruno Cardoso Lopes via cfe-commits]

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@@ -186,7 +288,7 @@ void CIRSimplifyPass::runOnOperation() {
   // Collect operations to apply patterns.
   llvm::SmallVector<Operation *, 16> ops;
   getOperation()->walk([&](Operation *op) {
-    if (isa<TernaryOp, SelectOp>(op))
+    if (isa<TernaryOp, SelectOp, SwitchOp>(op))
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bcardosolopes wrote:

Can you double check if the test passes without issues if `-DMLIR_ENABLE_EXPENSIVE_PATTERN_API_CHECKS=ON` is used while building clang? We currently having incubator issues with this and probably best to make sure we don't introduce them here if possible.

https://github.com/llvm/llvm-project/pull/140649