[clang] [CIR] Support __builtin_nondeterministic_value (PR #206149)

[Andy Kaylor via cfe-commits]

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@@ -2026,6 +2026,35 @@ def CIR_FNegOp : CIR_UnaryOp<"fneg", CIR_AnyFloatOrVecOfFloatType> {
   let llvmOp = "FNegOp";
 }
 
+//===----------------------------------------------------------------------===//
+// FreezeOp
+//===----------------------------------------------------------------------===//
+
+def CIR_FreezeOp : CIR_Op<"freeze", [Pure, SameOperandsAndResultType]> {
+  let summary = "Stop propagation of undef and poison values";
+  let description = [{
+    The `cir.freeze` operation takes a single operand and returns a value of the
+    same type. If the operand is a poison or undef value, `cir.freeze` returns an
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andykaylor wrote:

Nit: can you reformat this to fit in 80 columns?

https://github.com/llvm/llvm-project/pull/206149