[clang] [CIR] Add cir-simplify pass (PR #138317)

[Andy Kaylor via cfe-commits]

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@@ -29,6 +29,20 @@ def CIRCanonicalize : Pass<"cir-canonicalize"> {
   let dependentDialects = ["cir::CIRDialect"];
 }
 
+def CIRSimplify : Pass<"cir-simplify"> {
+  let summary = "Performs CIR simplification and code optimization";
+  let description = [{
+    The pass performs code simplification and optimization on CIR.
+
+    Unlike the `cir-canonicalize` pass, this pass contains more aggresive code
+    transformations that could significantly affect CIR-to-source fidelity.
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andykaylor wrote:

The phrase "could significantly affect CIR-to-source fidelity" is somewhat alarming. I don't think we're doing anything that changes semantics are we? I think this comment is about transformations that could affect ease of debugging. Perhaps we can word it more gently?

https://github.com/llvm/llvm-project/pull/138317